I was listening to the podcast rehashing the episode, "The Substitute" when all of this hit me. One of the questions (@ 15:40 in the podcast) that gets posed to Damon and Carlton was "If you had to choose which reality to live in: Island 2007 or LA X 2004, which would it be and why?"
Damon gives his answer, which isn't important, but then goes on to stress:
"You cannot treat these two things as entirely separate entities, they are NOT alternate time lines"
That's when everything hit me. If we are not actually dealing with 2 separate time lines, then maybe what we are dealing with, is 2 separate lives. Meaning all the Losties we have come to know and love, are all living out "new" lives in the Flash Sideways (FS). I wouldn't be surprised if we are actually seeing the reincarnated versions of all the characters living out their second chance at life. I think that there is a good chance that Jughead exploding in 1977 isn't the direct cause of the FS world, but something will happen towards the end of this season to explain the connection between these 2 realities. And in presenting the FS's the way they are now, they are actually giving us the Epilogue to this whole story, without us even knowing (Season 3 finale style).
We know, based on Damon and Carlton saying so, that these 2 realities will be related somehow, and that is something that will come later in the season, but the idea of the reincarnation makes so much sense to me. There have been several allusions to reincarnation over the series;
1 - When Alpert came to a young Locke presenting items and asking him which is "his" (same test as the Dali Lama)
2 - The van Ben was driving around off-island in season 4 had the name "Canton Reinier" on it, which is an anagram for reincarnation
3 - The many Ankh's we've come across, although don't represent reincarnation explicitly, they do mean "everlasting life" which can easily be interpreted to mean reincarnation
4 - And my personal favorite, Desmond's catch phrase "See you in another life brother". And wouldn't you know, Desmond DID in fact see Jack in another life, during this seasons premiere episode!
5 - There are a bunch more references on Lostpedias Reincarnation page.
I'm also going to make a bit of a stretch and compare Jacob to a Phoenix. When their time is up, they burst into flames, and are reborn from their own ashes. Ilana was sure to take his ashes once Ben pointed out that Fake Locke kicked him into the fire pit in the 4 toed statue. Maybe all the ash we've been seeing is actually Jacob's ash from previous rebirths.
I'm not sold on the idea that Lost's version of reincarnation is the same as the Hindu and Buddhist version, but overall, they have a theme of eternal life in the sense that you don't just get one chance.
Wouldn't it just be incredibly epic if this whole season, we were watching the epilogue of all these characters? Is it really possible to just end the series without an epilogue?
If the FS is actually the Epilogue of the Lost story, and we are in fact seeing everyone get a second go-at-life, it plays into exactly what Damon said in the podcast. These two realities are NOT separate entities, in that one life happened after another, which means, they are not alternate time lines. Even Juliet saying "It worked" could very well be her consciousness traveling into her next life.
We have invested so much time into all the characters, and I have faith that Damon and Carlton will wow us all with the ending, but in true Lost fashion, I'm sure the ending will just be a new beginning.