I find it funny there's so Little material left for the third movie.
Smaug devastates Dale, Bard kills Smaug.
Some psychology stuff in the mountain, the Arkenstone controlling Thorin, negotiations with the dwarves
Battle of the Five armies.
Wrapping up, and Bilbo going home.
+ the Dol Guldur storyline put in somewhere which I don't think will fill a lot.
I guess we will get a real time enactment of the Battle of the Five armies lasting 2 hours

Or PJ will come up with a lot of strange inventions of his own - like Kili getting elected for mayor in Dale before offering the seat to Bard or something.