Well hopefully the two Hobbit movies will only be 90-120 minutes each and not feel so bloated. I have no idea where to make the cliffhanger. Isn't the midpoint of the novel being captured by Beorn or something like that? Or maybe it could be the Gandalf / Necromancer battle as the first film's climax.
No, Beorn doesn't capture them or anything.
It's that....that IS the middle of the book, but the obvious "stopping points" are like...when they're fighting the Orcs in the Misty Mountains, but that's too early...
...and maybe the spider fight in Mirkwood...
....or maybe being captured by the Elven king?
...or Smaug's death