Yeah, I think anyone who thinks there isn't enough material in The Hobbit to sustain at least six hours probably hasn't read the book in a while. There are quite a number of little adventures along the way, but it's written with such brevity--for children, I might add--that things move on at a fairly rapid pace. Add to that whatever they've come up with for the White Council and Dul Guldur and I'm sure there's abundant material there.
My only concern has been where the break point between the films might be. The only thing I can think of is that they're doing a similar thing they did with Helm's Deep and the march of the Ents. There they took some events that were relatively low key in the book and really raise the tension and the stakes so they served as a worthy climax.