The purpose of this blog entry is not to present any new theories, but to give an update on where I stand with the flash-sideways timeline, based on what we've seen so far.
The last time I blogged about the flash-sideways timeline, we were only four episodes into the final season. At the time, I was running with the idea that the Jughead bomb explosion in 1977 caused the Island to sink, and that the alternate timeline contained the differences in people's lives as a result of the Island not existing after 1977, including Jacob not having influenced their lives. The few glimpses we'd seen in that timeline up to that point seemed plausible with that explanation. However, since then, we've seen flash-sideways differences that are just too difficult to explain -- Jack has a 13-year-old son, Sayid's brother married Nadia, Ben has a good relationship with his father (and Roger apparently chose to leave the Island with Ben at some point in the 1970's), and Sawyer is a cop with Miles as his partner (and Miles' father, presumably Pierre Chang, is apparently alive). This has to be more than just a timeline that split in 1977 when the Jughead bomb went off. And I've seen various Lostpedia bloggers offer other explanations.
I've seen a few Lostpedia bloggers suggest that the two timelines are, for the most part, mutually exclusive of each other. In other words, changes in one timeline didn't create the other; whatever happened happened in each timeline. In the original timeline, Oceanic Flight 815 crashes on the Island, the survivors eventually travel back in time to the 1970's, Juliet hits the Jughead bomb with a rock, and the bomb neutralizes the Swan station's electromagnetic energy. Events from that moment unfold as they always have, leading to Desmond failing to push the button, causing Flight 815 to crash. In the flash-sideways timeline, Flight 815 never crashes, and lands at LAX instead. The survivors never come to the Island, so when the Incident occurs at the Swan site in 1977, there's no bomb explosion to stop the release of electromagnetic energy caused by Radzinsky's drilling. According to this theory, the electromagnetic energy was what was keeping the Island afloat; i.e. it's not a regular island attached to the ocean floor, which explains how it is able to "move" when somebody turns the frozen wheel. The unstoppable release of electromagnetic energy causes the Island to slowly sink, giving people like Roger and Ben Linus, Pierre Chang, and Horace and Ethan Goodspeed time to evacuate the Island and return to the real world. The timeline from that point on is the world in which the Island resides at the bottom of the ocean. This does not explain all of the flash-sideways differences mentioned above, but I'll get to that in a minute.
So if the flash-sideways timeline is actually completely separate from the original timeline, then that raises the obvious question, what is the point of showing it, and what does it have to do with our characters in the original timeline? Things brings us to another theory that a few people have raised, particularly right after "Sundown" aired -- that the alternate timeline is actually a flash-forward, showing the result of the Man in Black giving the Losties what they want in exchange for their loyalty, as he offered to Sayid, kind of like a genie granting their wishes. He does this by creating the alternate timeline, starting at the point where Flight 815 is flying over the Pacific, creating conditions in which all of the same passengers are still on that plane, but for reasons which match up with the changes in their lives in the alternate timeline. This is the alternate timeline I described above. The MIB makes some kind of deal with the Losties and places them in that timeline which contains the situations that grant each of their wishes. The catch is that they retain no memory of their previous lives. But it wasn't a perfect memory wipe, because the characters still have a sense of familiarity with each other -- Jack recognizes Desmond, Sayid stops by to help Jack break open the bathroom door, Sawyer helps Kate escape, Claire trusts carjacker Kate, Hurley helps Locke get a new job, Jack is confused about when his appendix was taken out.
If this theory is correct, then it still leaves the question as to how it's going to play out in the alternate timeline -- whether this is truly the end of their story, or if something is going to reveal the truth to them and they have to somehow make things right... which would be a pretty big challenge convincing each of them, considering that they seem to have happy endings in every episode so far, so why would they want to go back?
Of course, now that I've written all that, I'll probably be shown to be way off-base again in a couple of episodes.