Though there's no director hired for the last chapter yet, the latest news is that Summit wants Chris Weitz to direct, and they may split Breaking Dawn into two movies, like the treatment of Harry Potter and the Deathly Hallows. Screenwriter Melissa Rosenberg is attached to write Breaking Dawn (hopefully she sees this letter).
If Weitz takes on the last film, he'd be the only director to helm more than one Twilight movie, and though I thought that he handled the special effects in New Moon very well, he's expressed trepidation at the idea. I'm not opposed to a different director taking on Breaking Dawn, personally — I'm anxious to see the job David Slade does on the more physical Eclipse; he might impress more than Weitz. And of course, a completely different, fourth director is intriguing as well. What do you think?