Even if Jackson cut out all of his extra material I still dont think a single 3 hour film would have been enough. Sure it could have been done but the cutting and condensing would have been excessive. And I doubt the end result would have been the most satisfying thing.
I think the page count of the Hobbit fools a lot of people. Sure its short. But the reason its so short is because Tolkien summarized a lot of the scenes and action in that book. The page count of that book is very deceptive when you start looking at the story and the size of the set pieces and story beats. Its a simple story but it actually covers a lot of ground and unless you want a film that spends about 5-10 minutes in each location and reduces the Battle of the Five Armies to a 10 minute skirmish I dont see any way of doing it in one film.
Even Del Toro thought two films was ideal. They tried going the one film route and having a bridge film, but then they dropped the bridge film and decided on two Hobbit films because they didnt see a way of doing a satisfying single Hobbit film.
But like I said I dont think a single film was impossible, but it was not ideal and it is the opposite extreme of what we've got now. Instead of people fussing about excess we'd have people fussing about there not bwing enough of this or that and character's like Beorn being cut among other things. Two films was the perfect middle ground.
That being said, Im hoping that once BTFA is out and all 6 films are watched together they function well.