Three Time Lines. LOST ended with The Incident by Malatesta

The writers talked of ending Season 6 with enough information for fans to piece together what the show was about. They also said that their response to fans wondering about what happened when the bomb exploded was to create two timelines to show both alternatives, and flash sideways.

However, so many answers have been provided of late that fan theories are converging, based on the idea of this island contest for Jacob to prove MIB wrong, by showing human nature choosing good in the face of satanic temptations to get what they most want.

Arguably that happened in the finale to season 5 when our heroes decided to blow up the island and never crash for the sake of erasing all the suffering and death that occurred since then (knowing nothing about this contest between Jacob and MIB at the time,and giving up what they most wanted--Kate holding on to her loves of Jack and Sawyer (and freedom from the law), Sawyer holding on to Juliette and vice-versa, Miles reuniting with his dad perhaps. That proved MIB wrong. The newcomers didn;t all corrupt and destroy and the rest.

Now three time lines are going--the island story, the back to LAZ and LA story, and the sunk island story that resulted from the island losing its purpose, its contest. (Some think it went the other way--the future, after Flocke wins.

Season 6 then, may be something else, I know not what. But being something other would certainly allow the writers to throw the sorts of curves they threw in the first five seasons.

Perhaps it explains who Jacob was in the cabin or who that was in Jacob's cabin--certainly not the Jacob or MIB we know. Perhaps it reveals the back story, perhaps a Zoroastrian one of what divinity apparently set up the cosmic good-evil conflict choosing Taruwet and Smokie perhaps as the first candidates to play it out, then transferring their powers to mortals. Who knows