I think a bit of it stems from the fact that the game was utterly unplayable at launch. Those who are left in the community are the masochists that stuck with it. In the early days you could spend a full night trying to play a single full game and be unsuccesful. The state of the game has now reached the point where it's relatively reliable, but there are people who feel entitled because they suffered through those first ugly days. There's a feeling that if the game had not been crippled at launch there would be a more vibrant community and there would have been more updates, presumably because SD and GPG would have tasked programmers to work on new content instead of fixing the netcode.
So in a sense, I feel we probably missed out on new DGs and maps because the launch was a mess. It's now pretty obvious that Demigod is dead in GPG's eyes and Stardock is going to back out of it as well. SC2 is being published by Square Enix and will be available through Steam. So it seems that the relationship between GPG and SD is at an end. With that in mind, if you're not happy with DG now, I wouldn't hold your breath for any big updates from here on in. In fairness to both GPG and SD, there are no sound financial reasons for doing so.