This is info taken from the article that started the whole James in The Hobbit rumor.
"As far as scheduling goes, Jackson said he will spend the rest of this year writing - along with his LOTR writing parters Fran Walsh and Philippa Boyens, as well as del Toro - with 2009 dedicated to pre-production on both films and 2010 when the films will be shot back-to-back; The Hobbit will be released December 2011, with F2 following in December 2012."
http://geeksofdoom.com/2008/05/24/jackson-del-toro-reveal-hobbit-details/




Here's the IMDb page:

