At the very least Del Toro wouldn't have tried to milk the book for a trilogy.
So many people are thinking this happened, but it didn't. The deal was to make two movies. The studio only planned on two movies. And Peter Jackson filmed material for two movies. Then when he was done, Jackson decided that there was too much material that he had to drop from his original vision of the story that he wanted to film, and there was some material from the Appendices that had never been in his vision but he wanted to film that too. Basically he was being a Tolkien fanboy
He didn't decide "I want to do 3 movies, let's see what I can do to make the story fit", in fact when he first brought up the extra material he still wasn't sure how it could be done, because the two movies were complete, and there wasn't enough remaining material for a stand-alone movie. He was even considering filming that stuff for an Extended Edition of the two Hobbit movies. In the end he decided that the best solution was three movies with the new material spread throughout the last two, and of course the studio went "A THIRD BILLION DOLLAR BLOCKBLGRFDROOL... ahem, I mean, yes, you gotta do what you feel is best, we'll support you."