Robert, Kristen and Taylor Lautner have become much more popular than they ever dreamed of becoming.
There is only one more movie to make, Breaking Dawn which they will most likely film in two parts. Filming in the movie in two parts is not in the contracts of the actors and so they are thinking about renegotiating the contracts to make more money for the time they will have to take away from their busy schedules to do another film. Remember, since Twilight, these actors have risen to fame and have been working non-stop since then.
This is why Taylor Lautner, Robert Pattinson and Kristen Stewart will ask for more money for the use of their character and image. After the huge success of New Moon, it is only natural that the three actors should ask for more.
We hope the producers and the actors come to an agreement, because if not they would have to find three new actors for the Breaking Dawn movies and what a disaster that would be!