E! Online chatted with Ron Perlman, who says he thinks they will start shooting Hellboy 2 in the fall. He also commented on a possible trilogy:
You know, you make them one at a time, but I would say that if there are more Hellboys in the future, then I’m very blessed, because he’s a guy I could play every day for the rest of my life and never grow tired of.
Source: E! Online