I have this theory about how the episode format will be for Lost’s next season, Season 5 (S5).
I believe that there will be two distinct narrative timelines, one in the island with the remainder of people, and one off island with the Oceanic 6, Ben and possibly Desmond/Penny. There will be very few flashbacks, possibly no more than 4-5 for the whole season.
The off-island story will stop being out of order, but it will pick up from the S4 finale’s flash forward (which will take place after the S3 finale with Jack trying to suicide). From that point on, the story off island will be as narrative and in-order as the story so far in the island has been. So it won’t be a flash-forward anymore, but what viewers will perceive as “current”. The on-island story will continue to also be narrative and current, but with a catch.
Remember that on the latest episode Locke said that they need to “move the island”. I believe that the “movement” won’t be necessarily in space, but definitely in time. As you might know, at least 3 years have passed by the time the Oceanic Six were rescued and Jack tried to suicide. Even when taking the island’s time displacement into account, you can’t hurry up the storyline by 3 years in a single season on-island in order to match the off-island storyline. That won’t fly with the viewers because the on-island story is the default story.
You see, at the end of S5, we will see the two stories/groups merge again, as the off-islanders will have made it back to the island for the final act in S6. This leaves no alternative to the writers but to have two in-order narratives that their timeframes will match at the end of S5. And this can only mean one thing: time travel for the whole island in order to match the off-island timeline.
As for S6, I don’t expect many flashbacks either, except maybe a few Dharma-based ones. Flashforwards won’t be relevant anymore and flashbacks won’t fly either as the story is not about a few survivors as it used to be in S1, but a whole lot more.