So they have changed it to 3 movies now. On the topic of Characters that were not in the book yet have been confirmed in casting.. I.E. Aragorn, Saruman, Radigast etc. I think they will depict The White Council's attack on Dol Guldor. The Necromancer in Mirkwood. This happened while Gandalf was away from the Dwarves. It's why he's not with them in alot of the story. That storyline would include all the big roles and would not break from canon. It would also be super cool!