I don't think they should make a sequel just for the sake of it or to fulfill some studio's profit projections. I do think there's enough to create a unique story that could stand on it's own merits. I havent read any of the comics, so i dont know where it is in the story line, but it would make sense to have hit-girl, kick-ass and red mist return. It seems like its still up in the air, but i for one hope they make a sequel. i just hope it has the same sense of integrity the first one had and i know mathew vaughn wouldnt do it otherwise. then again, if a studio has the rights, it will get made one way or another.
"Convex world is caving in. Left the life to let you in, but now...your story's out."
From the song "Broken Glass" By Grey Magic (Me)