According to Deadline Hollywood Daily:
The Hobbit and its sequel will finally be made back-to-back for New Line and MGM the way they should be — under the Academy-Award-winning creative vision of Mr. Lord Of The Rings. But Jackson won’t be directing this time out, because of his previous commitments to DreamWorks for The Lovely Bones and Tintin trilogy with Steven Spielberg. While that will disappoint his LOTR fans, they’ll be pleased to know that the famed director will be integrally involved as executive producer along with his partner Fran Walsh. I’m told Jackson will make all creative decisions in concert with New Line, which will manage the production of the films.