Wow. Okay, here's what we know for sure. It is possible to get off of the island. At least Jack and Kate do.
What we don't know...
What is the Island, Where is the Island, When is the Island? (I think this last question is extremely important.)
Let me first say, at the very first "flashback", I believed it was actually a flash-forward. And stuck with that until the moment Jack told the new chief doctor to get his dad down there, but, after all we'd seen him walking around on the island, right, he could still be alive. The Island cured Rose, cured Locke, and allowed Jin to have a baby, couldn't it conceivably have brought Jack's dad back to life as well? So I wasn't too surprised to see Kate meet Jack.
Now, of course, everything has changed.
What does the show become? Do we go to the future? Does it become about Jack trying to get back to the Island? Does it pick up on the island with the rescue and we see how Jack gets to this point?
Either are possible.
Important things to keep in mind: one, they supposedly found the plane and there were no survivors. Okay, this info came from Naomi, and I'm not sure how much she can be trusted since Penny claimed to have never heard of her. But somehow she knew about Desmond and Penny, and somehow she knew a little bit about Charlie, at least. Is it possible that Benry Gale isn't the most evil person our Losties can meet up with? That perhaps there is a more sinister force (that Benry Gale really feels are the "bad guys") out there with far more information about the island and the plane? I think that it's likely. Two, not only is Jack's dad still alive in the Flash Forward, but Kate is not (apparently) a fugitive. Three, Jack says to Kate, I'm tired of lying or something to that effect (as Locke says, I'm going to have to watch that again), what did he mean by that? And, finally four, at the viewing, when asked if he is a friend or a relative, Jack says neither. If, assuming as I am, the viewing was for someone else on that plane, why does Jack not say friend?
Okay, now, it has only been about 25 minutes since the episode ended, and I'm still theorizing as I'm writing, so a lot of this isn't as developed as it will be once I think a little more on it, and talk to a few more people. But here are my new theories...
1. The show picks back up on the island, but instead of flash backs, we start to get flash forwards to a possible (maybe even certain) future. For instance, we start on the island right where we left off, but there are still some things to be done in order to get everyone off. There are still all of the other Others, who might have something to say about it, and we know Locke doesn't want to go. Was that really Walt or the Island/Jacob manifesting itself/himself as Walt. If the Island/Jacob doesn't want them to go, isn't there more it can do to at least stall them? I believe so, and it won't be super simple to get off of the Island, so we'll get episodes on the Island interspersed with flash forwards to what happens after the Island.
2. I believe that the Island is in another Dimension. I believe that in the dimension that our Losties are from, Oceanic Flight 815 really did crash and they really did find all of the survivors dead. I believe that it's possible, in the right circumstances, for you to die in our reality, but simultaneously appear on the Island. So that brings up the question (if I'm right in Theory 2) of how is the found plane and dead bodies explained away with the reappearance to his former life of one Dr. Jack Shepard?
3. I believe that in order to get off of the Island some sort of dimensional travel is involved, which only makes sense since I believe that the Island itself is in a separate dimension. Now, with dimensional travel (according to some theories in physics) there is also time travel. In order to get everyone off of the Island, Dr. Jack is going to be offered, I think, some sort of deal. It will involve going back in time before the flight happened. It will involve going back to their lives as they left them before the circumstances that caused them all to get on the flight.
4. Okay, we have been shown in the flashbacks these last three seasons the fact that everyone on that flight was somehow connected far more then your usual "6 degrees". In the recap episode "The_Answers" we were told that the connections are part of what caused everyone to be on that flight. In other words, it wasn't an accident that got those exact people on that exact flight. The creators used the example of Anthony Cooper, Locke's father. If not for his actions, Locke would not have become the man that he did, and Sawyer certainly wouldn't have become the man that he did. By conning Sawyer's parents (and causing their death) and by throwing Locke out of an 8 story window (and paralyzing him) he led directly to the events that put each of them on that plane. Locke was trying to prove he could still be someone productive despite his paralysis, and Sawyer following a lead that he thought would take him to the man that killed his parents. It isn't too big a step to think that if the events don't lead to the right people getting on that plane, then that plane won't crash.
5. So, this is explained to, at least, Dr. Jack and Kate, and most likely one other whose funeral it is that Dr. Jack goes to. They go back to the past and have to make decisions that change whatever the reason is that they would have gotten on that plane. And in doing that, the plane never crashes. That means, that they save EVERYONE. Not just the other Losties that are still alive, but everyone who perished in the crash as well. And everyone who has died since they survived the crash. Eko, Ana-Lucia, Libby, Boone, Shannon, and Charlie would be alive. How could Jack not agree to this. Of course it would mean that only they (at least Jack and Kate) would remember. In addition to their lives back, they get passes allowing them to fly free wherever they desire.
I know, that's the big one, theory number five. Let me give you some of the reasons I came to this conclusion. Jack says that he's tired of lying. This would explain that. What might happen if everyone were returned to before the crash? Well, Charlie would still be addicted to drugs, and nowhere near the fame he thinks he desires. Of course we know what he really desires, but we also know without the crash he doesn't really have any hope of achieving it. And I think he was resigned to his death, he definitely didn't go into it blindly. Which do you think he'd prefer, having died a hero and having known and loved Claire and Aaron, or continuing in his drug addled unfulfilled life as a former rock star? Eko would still be a fake priest living with that guilt as well as the guilt of having killed his brother. He came to terms with his past actions due to the Island, but I'm not sure he could have gotten there without it. Rose would still have cancer. Sun and Jin would still be in a horrible and unhealthy marriage. Boone would still be helplessly in love with his step-sister, and she would still be using it to torment him. I could go on and on, the point is that the experience of the crash has actually improved these peoples lives. If they were placed back in those lives with no memories of the crash and their experiences there, they are right back into those awful situations.
Now we know that Dr. Jack and Kate at least still remember what happened to them, right? So, one could assume that their lives are better because of what they've learned. Obviously not, in Dr. Jack's case at least. He's bottomed out. A huge low, even for him. What could have brought this on? If I'm right, he had to change the decision that led to him getting on that plane. That means he had to keep from getting his dad fired. If his dad doesn't get fired from the Hospital, then he doesn't drink himself to death in Sidney, Jack doesn't have to go get his body, and they don't crash. Plus this would explain how Jack's dad is still alive.
Okay, Kate. If she isn't a fugitive, she can't get caught and brought on board the flight. Therefore, she can't kill her stepfather. Now, remember, not only was he hurting Kate's mom, but it appeared he had the hots for Kate as well. If he's not dead, couldn't he have some hold on her. Enough that when she goes to meet Jack, she has to say to him, I've got to get back before he notices? I'm betting that she was referring to her Stepfather.
That brings us to the mystery person, the one with the funeral. I think they know as well. So, who are they? Well, Jack goes and answers the man's question of friend or family with neither. There's really only one person that would elicit that response from Jack. Sawyer.
Not only that, but he was hoping that Kate would be there. (No doubt they've had a falling out, however. It was pretty well foreshadowed in the episode that a Kate/Sawyer falling out was in the cards.) If Sawyer's back in his previous life, all he has to do is not go kill the person that wasn't the real Sawyer anyway. Easy enough. But that doesn't change the fact that he's not in a good position, and there are no shortage of people that want him dead, even with a memory of everything that happened, and the knowledge of who the real Sawyer actually is.
Now, Jack has gotten everyone safely home, but what if while using the pass to fly all over the place, he starts reconnecting with the other people who were supposed to be on that plane. They would have no idea who he is, of course, but he would know them. He would begin to see what horrible shape they were all in, especially the people who died on the Island. He would begin to understand that they would be better off having died there then living the lives that they had left behind. Perhaps he would come to understand that they had died as better people on the Island, and because of the Island, then they ever could hope for if they hadn't had that experience.
With me so far? Okay, the obvious question becomes why don't Kate and Jack end up getting together? They both know what really happened, and they clearly feel for each other. This, one would think, would especially happen if there was a big falling out in the Kate/Sawyer relationship. My theory is that the trip back in time also gives Jack the chance to fix the relationship with his ex-wife. He goes back to before they get divorced. Benry Gale asks him what he has to go back for, his wife had left him for another man, but what if the trip back took him to before that happened. We know how much Dr. Jack likes to fix things, don't you think that this would be something he couldn't resist? Now, we know that it doesn't work, we see that in the Flash-Forwards. Failing at his marriage again, when he knows that the trouble is coming this time, combined with the state of affairs that all of the other former Losties' lives are in, and finally the death of one of the only other two people who knows what really happened cause his to finally hit rock bottom.
These are my thoughts. Can't wait to talk to more people, see what they think. Once again, however, this show has changed everything. The fact that this theory is so completely different than anything I had previously posted or even thought about, shows you how amazing this show has the capability of being. Whether my theories prove to be completely, partially, or not at all correct doesn't change the fact that I'm glad I've been along for the ride so far and can't wait to take the rest of the way. 48 more episodes until everything is made clear.
Until Next Time, I'll see you in February LOST.