if there's a problem with the Mask, it's this: dark horse is a comic book company when the creators own the rights to the material..Kinda like Image Comics.
The Mask hasn't had an on going series in years because the creator is probably over it and moved on. I would like to say about 10-15 years, and as the time goes on, the fanbase gets smaller and smaller. I love smaller comic books, but I think it would make more sense to do a movie based on..The Goon or The Walking Dead. Something that's on-going still. Heck even Ninja Turtles and Archie are still going on.
My point being is that if the demand is strong enough, then maybe we can get a reboot. Sames goes with The Crow. Anything can happen. For God's sakes, Rob Leifeld's Youngblood is getting a movie so anything goes.
Anyway, I want to say that Nine Line/Warner Bros let the license expire and went back to Dark Horse and/or creator.