He answers this and other questions over at AOL
14. What's next with 'Dr. Horrible' -- a sequel, a movie? When we made the 'Sing-Along Blog,' it was sort of an origin story, so I assume that there's a future with it. I just know that Joss [Whedon] is insanely busy with 'Dollhouse' and launching that show for Fox, so I can't imagine when it would be able to happen. But I know they would love to see a future with it. I wish I had concrete information, but everyone desires longevity with it -- in what capacity I have no idea. Maybe a big, giant Vegas show! Then we'd really have all the special effects ... laser beams and contortionists.
You know I can't resist Dr. Horrible. In one way I don't want them to ruin it but really I just want more!
(Neil Patrick Harris photographed by Eric Schwabel)
***UPDATE*** Dr. Horrible Available for Pre-order now!! Release Date Dec. 19th! What's up bitches??