While there's been no official decision, Joss says star Sarah Michelle Gellar wants to concentrate on her movie career.
CBBC Newsround Online reported back in August that the high-kicking actress wanted to do other stuff after she starred in the Scooby Doo movie.
Joss says: "She has been doing Buffy for seven years, so if she did decide that this was her last year, it's certainly a decision I'd respect."