Long-running, serialized shows love doing something with their final season (when they know it’s their final season, at least): go back to the beginning. What that means exactly can vary from show to show. Example: On Buffy the Vampire Slayer, much of the last season surrounded Sunnydale High School, the primary setting for the first three seasons until it was ceremoniously blown up. On top of that, the big bad of the season is “The First” (or “The First Evil,” which can appear as the visages of the dead foes and allies of the show) - giving double meaning to “going back to the beginning” in a single show. The last episode even has Giles repeating his final line from the pilot: “The world is definitely doomed.” The point is, it’s cyclical, which gives the writers the opportunity to deepen the themes and show how far (or how specifically not far) characters and situations have come. Gilmore Girls (forgive me) ended with the same shot that closed the pilot. Arrested Development’s finale echoed its pilot in many, many instances as well.
And now Lost is going back to the beginning - or actually, before the beginning (or ACTUALLY after - depending on what you consider to be “the beginning”) - to the flight of 815. Except this time - it doesn’t crash on Craphole Island. That key moment that set all of the plotlines into motion doesn’t occur - the impetus for the series is gone. All that remains is the depressing memories held by Jack, Kate, Sawyer, Hurley, Sayid, Jin, Sun, Locke, and possibly a few more (or less). Why would these people remember, while others will not (Michael and Walt almost certainly will not be seen nor remain part of the story, Michael because Harold Perrineau felt burned by his lackluster, short-lived season 4 return, and Walt because the kid is now 6’2”). Maybe Charlie will figure in briefly (he has been confirmed for at least a cameo appearence), but he won’t be a major player. Those that remember will have to work together to comprehend what exactly they went through and what needs to be done.
Which begs the question: what does need to be done? Return to the island to save Jacob? Kill NotJacobSpirit? How “good” were things while Jacob was around? Do we even know for certain that it was him who did all of that island-healing that Ben was always talking about? Remember: Ben had never even seen (nor met) Jacob. In fact, the place he thought Jacob lived was home to NotJacob! Maybe NotJacob was the force behind the healing? Maybe it was neither - just the natural magicness of Craphole Island? Although I am certain that the murder of Jacob was an event so cataclysmic it would essentially mean the end of existence (which is the reason Jack and Co. had to return to 1979 and blow up Jughead to turn back the clock), I can’t help but wonder what we actually know. It’s astounding that after five seasons we may actually know less about this show than when we started, purely because we’ve been mislead by characters who themselves were mislead by other mislead characters.
Regardless, we’re going back to where it all could have started. This solves one of the central dilemmas of the show (almost): the regret the characters hold deep within themselves. The flashbacks were primarily to show mistakes the characters made and the baggage they bring with them everywhere they go. Now they actually have the chance to fix some things, even though many will NOW have regrets over events that haven’t even happened yet (and may never even happen), e.g. Jack’s lament over ruining things with Kate off-island. Both know about the issues, even though the events never occurred now. Sayid can find Nadia now and hopefully not cross any dangerous streets, Michael can be a good father to Walt, Jin and Sun can be happily married, etc. Some can’t be fixed though - Jack can’t make peace with his father, Kate can’t gain her mother’s sympathy (and now she’s on the way to the clink), Hurley can’t un-win the lottery.
There’s going to need to be a lot of legwork done early on to get the band back together and back to Craphole Island (wasn’t that the plotline LAST year?!). Getting Kate out of government custody, convincing Claire to come along (Aaron needs to be raised on Craphole Island - destined to be the vessel for Jacob or NotJacob? Still potentially!), figure out how the hell to handle Ben (who is still on the island, but now with no - or very little - Juliet, given her starring role on V) and Desmond (now that the Swan set is gone and his mind is un-flashed).
It’ll be interesting to see what the castaways (or non-castaways I guess) find their ultimate goal this season, and what the show’s ultimate goal really is. If it’s about Jacob, it would just feel strange, given we really just met the guy and still know less than nothing about him (other than him being a stabbable ghost). We’re back where we started, but the finish line is quickly approaching, and that is the important thing.