As has been mentioned, GC2 uses an older compiler which is not supported under Windows 7. Migrating it to a newer compiler would take time, money and people. It's possible to run the older compiler in a virtual machine on Windows 7 with a bit of kajiggery, but that presents its own set of problems and still requires time, money and people.
Plus, even if you can fix the problems you have to test to see if you haven't just gone and introduced a whole new set of problems. If I had even just five testers playing games with the latest mod and sending back useful information, I could spend more time actually tweaking tech trees and improvements and so on.
Put simply, when the AI makes a bad decision about which tech to go for (and deciding whether it is bad can be somewhat tricky) I have to look at why it valued that tech wrongly. Then I have to figure out a way that it will still pursue that tech, but not before some other tech. Then I have to rinse and repeat. Now it is possible to accelerate things by letting the AI play against itself, but after a certain number of turns the interface locks up with several screens trying to open at once, and it's impossible to break into the turn cycling and examine the AI's current research project. Plus, the AIs do not experience the same pressures with no human player in the game. I play the best I can, without too much accelerating of turns, to expose the weakness in their strategy, and then fix it.
I don't know why Stardock hasn't given us an inkling about their plans for GC2, but the game's got plenty life left in it yet, as long as people don't give up on it entirely.