There are three episodes on the DVD set that were never broadcast, and he's written a movie script for it that's been purchased by Paramount, but the project has not (yet) been greenlighted.

On the DVDs, there are some interviews, and one of the interviewees (a bigwig production guy, IIRC) says that the best of all worlds would be if the movie was made and then some network might pick up the TV series again.

FWIW, The Family Guy was picked back up after being cancelled due to exceptional DVD sales. Firefly's DVD sales have also apparently been outstanding. Of course, Firefly's bound to have cost a lot more.