Apparently, there is now confirmation that Peter Jackson and Fran Walsh will direct two films based on the Hobbit.

Why it's two flms, I'm not sure... maybe they're going to have content that isn't in the Hobbit itself, but happens at the same time and is in Unfinished Tales, the Silmarillion, etc.

but the story can be read here:
http://www.thehobbitblog.com/