It appears that Britney Spears may have a short appearance in High School Musical 3: Senior Year. Kenny Ortega director of HSM3 is apparently trying to make it a happen.
The movie is supposed to feature a parody of Britney Spears’s "Baby one More Time" music video, and as a result Ortega wanted to get the actual Britney involved in the production.
Her role is not yet determined, but it is unlikely she will play a High School student.
High School Musical 3: Senior Year should be out in the fall of this year.