Apparently all of the speculation that Taylor Lautner would be replaced in Twilight follow-up New Moon (because he did not look mature enough to play the older, more mature Jacob Black that is meant to appear in the film) was much ado about nothing.
Author Stephanie Meyer has confirmed this on her website with a statement from New Moon 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.
I imagine this makes many of you very happy...