The original developers formed an independent company called Toys For Bob and bought back the rights to all but the Star Control name, then retitled the game as "The Ur-Quan Masters" and released everything as open source. They've been talking about making a true sequel for some time, but then they were bought by Activision and apparently put to work churning out cheap movie tie-in shovelware. I'm not sure what the problem is exactly, but I suspect that either Activision now owns the rights to Star Control, or Toys For Bob just doesn't have the time to work on it without it being their official project.

They tried a petition a while back, but it didn't work. Now they've got a giant map in their office filled with pictures of SC2 fans who want a new game, and every time Activision shows up they make them look at it.