I dunno, my wife and I have been feeling the opposite.... Considering how far they've come this season (nearly concluding the story of the survivors' lives from the crash to the 'rescue'), I'm having a hard time figuring out what the heck they will fill another 2 seasons with! I've always imagined the "end" of the show would coincide with the rescue of the survivors. That arc seems to be concluding within this very season. I don't know if I'm interested in 2 seasons of LOST that take place back in the homeland, dealing with the survivors sorting out their 'issues' and what not. Two seasons is a looong time, I don't know how they are going to fill it out.
This is what is so exciting to me! Why this show is so good. They keep playing with audience expectations, keeping us guessing. I don't even know if the flashbacks/forwards will continue or if they will just cut between the island happenings and the rest of the world next season. I think they have well in hand and have mapped out the major points for the next 2 seasons in order for it to come to a natural conclusion. All I do know is that it will not be a happy ending for several of the characters and that some people are bound to be disappointed with the reveal of the 'big mystery'. I can't wait to buy the whole series box set on Blu-Ray!