here is some info from wikipedia about the third season:
Season three will begin airing October 4, 2006. It will include 25 episodes that will be delivered in two blocks: an initial fall arc of seven episodes and a second run of consecutive episodes beginning in January or February. According to executive producer Damon Lindelof, there will be new characters in this season as the fans get to know more of the 48 survivors. There will be fewer flashbacks of the original characters since the new ones will have their own that will become a unique and central component of the series.
i thought season 2 was a bit..uhm...'awkward' in places, but of course im hooked. i somehow think that the should come to an end...there is only so much you can do..