The producers of FlashForward have claimed that they already know how the series will end. Not exactly spoilers, but it's good to know, right? :)
Speaking to SFX, David S. Goyer, said that he has meticulously planned the end of the show:
"We pitched [ABC] a fairly excessive plan," he said. "I mean, we know exactly the shot that season one ends on! They obviously said this resembles Lost, in that it's a really cool script, but [they asked], 'Do you have any idea where it goes?'
"We said, 'Yeah we know how the whole season ends and how the whole series ends', and they went, 'Holy s**t!'"
Producer Marc Guggenheim added:
"We know what the ultimate season is and the penultimate season is. For in between, we know the various seasons but we are treating it like an accordion.
"In success, [the show] can go seven years. In less success, it would need to go three years to work. The end game of the show, to be properly done, really requires two full seasons focusing on the end game."