Lost was never forthcoming with crucial information. If there was a fire under your ass, Lost probably would have let you know, but it may have taken them a year or two to finally give you all the necessary information. One tasty tidbit it did manage to give us after implementing flash-forwards (when it realised that everyone was kind of getting tired of its crap) was that sometime in the future, John Locke would die, and that would prompt Jack and the other members of the Oceanic 6 to have to go back to the island for reasons I don't have the space to fully explain. This was a large surprise to die-hard Lost fans, as no one particularly wanted Locke to die or could imagine how the show could possibly go on without Jack and Locke yelling at each other all the time.