Taylor Lautner has been confirmed to continue his role as Jcob Black in the movie version of New Moon:

Good news about New Moon from director Chris Weitz:

I'm very happy to announce that Taylor Lautner will be playing Jacob Black in New Moon and that he's doing so with the enthusiastic support of Summit Entertainment, the producers, and Stephenie Meyer.

The characters in Stephenie's books go through extraordinary changes of circumstance and also appearance; so it is not surprising that there has been speculation about whether the same actor would portray a character who changes in so many surprising ways throughout the series. But it was my first instinct that Taylor was, is, and should be Jacob, and that the books would be best served by the actor who is emotionally right for the part. I think that fans of Twilight the book and the movie will be surprised by the Jacob Black that Taylor will bring to the screen in New Moon; and I'm looking forward to working with him and the rest of the cast in realizing the film.

very best

Chris Weitz
http://www.stepheniemeyer.com/index.html

At first I wasn't convinced that Taylor would be able to pull it off with the huge changes in Jacob in New Moon, But I really can't see anyone else playing him either. Besides, Taylor has a HUGE following and I think it could potentially affect ticket sales if they recast him. I'm really looking forward to seeing what Chris Weitz can do with it.