To go along with Tarantino’s talk of a sequel to Kill Bill in 15 years, he’s also floating the idea of an animated prequel to Kill Bill:

… focus on the three men – pimp Estebian Vihaio and martial arts masters Hattori Hanzo and Pei Mai

This same little IMDB article mentions that Quentin will be directing a portion of Robert Rodriguez’s next film, Sin City. In order for that to happen, Rodriguez actually had to resign from the Director’s Guild because of an arcane rule about one director, one film. [Hat tip to Eric for the Rodriguez story]