Yeah, I'm gonna disagree with Arthur on this one. True that The Hobbit was originally meant for children, but I just reread it with an eye to wondering what PJ was going to do, and there is more than enough room for expansion.
Also, just calling it The Hobbit is almost a misnomer, because Jackson is going to follow Gandalf's entire journey while he was away from Bilbo and the dwarves. That's an entire movie of plot right there.
If Peter Jackson is going to Middle Earth, I'm there. One movie, three, film the Silmarillion, just tell me when it's in theatres so I can arrange a babysitter.
Of course, I'm one of the nutters who bought all 12 slush books which Christopher Tolkien assembled, so I'm not exactly the average fan. :)