I'm going to guess that neither movie will be three hours long like the theatrical editions of LOTR were (except for ROTK, which was even longer). I also think that An Unexpected Journey
will end sometime shortly after the Company escapes from Goblin-town and Bilbo steals the Ring from Gollum, and then There and Back Again
will cover the Company's adventures in Mirkwood, Lake-town, and the Lonely Mountain. Again, though, that's just a guess on my part.