LA X Parts 1&2 were mind-blowingly filled with set-ups for LOST's final endgame. I have found that two scenes toward the end of the premiere have been shown to set-up the series finale.
Before I get onto those scenes, let me throw out a quick theory about Juliet's death.
Juliet died saying "We should get coffee sometime. We can go dutch." She also communicated through Miles that "it worked."
I predict that in the Crashless Timeline, Sawyer will "meet" Juliet and they will hit it off. Juliet's mind was simply traversing through universes. I foresee an episode in which Juliet's outrigger shoot-out will be shown from the other side of the ocean and she will end up "saving" James.
Okay, so onto those 2 important scenes.
The translator tells Jack that they need to talk in PRIVATE. This idea of Privacy shows that none of Jack's friends can know about what he is told. I think that the Others are going to send Jack back/forward to the Crashless Timeline. Therefore, the opening scene where Jack sits on 815 is a Flashforward from Jack's perspective. He needs to "redeem himself". So what has Jack done that needs to be redeemed? Well, by certain actions, Jack caused the Death of John Locke. I think they will send Jack back using some sort of mystical device and before it, he recieves the slight gash on his neck. Jack is told to not interfere with the lives of anyone. He is FULLY aware of what is going on in the alt-universe. He just didn't expect Desmond to pop up. So, in order to NOT reveal his secret mission, Jack simply asks Desmond if they know eachother. It is Jack's way of seeing if Desmond is aware of his agenda.
So how is Jack going to redeem himself for the Death of John Locke?
Well, in the Crashless Timeline, Jack offers John a free consultation. He wants to fix him. I believe that the series finale, and Jack's mystery consists of Jack having to perform surgery on John Locke.
Jack will make John Locke walk again. And not just in the Crashless Timeline. The redemption of saving John from a sad life will result in his true ressurection on the Island in 2007.
Nothing is Irreversible.
Dead Is Dead...or is it?
These two themes seem to contridict eachother. Jack's mission is to "save" John Locke. In more ways than one.
This series has always centered on the relationship between Jack and John. I foresee the final image of the series being Jack's success: Jack will fix John's paralysis in the Crashless Timeline and on the Island, the deceased John Locke will rise.
The series opened on Jack's eye opening.
The series will close on The Deceased John's eye opening.