This is what Guillermo del Toro had to say on a second Hobbit film's prospects (via):
"We believe there is a second movie... If there isn't, there will not be. If we find it, we will shoot it, but by God, if we do not find it, we will not shoot it. I am anxious to shoot the book, and I'm willing and able to dedicate myself to shooting the [second film].""
I have no idea what he just said. He's stoned.