wodmarach: Theres a couple of insider rumours floating around that when they got hold of the assets etc they had to decide between throwing it away or fixing the bugs and punting it out the door... they decided that rather than make it go another 3 years and spending even more on it they'd punt it out and depending on sales make a proper game..
The problem is that they've now locked in several things that had they just bought the IP they wouldn't be lumbered with. Firstly there are the expectations regarding quality. Those have now plummeted. From all that was expected from DNF to the sad reality. It has been a harsh fall.
Secondly there is the fact that they've also locked in expectations regarding content. They could have come up with something more like Serious Sam with DN3D's more open exploration-encouraging maps. But instead they created an extremely linear cover shooter that in no way contains the strengths of the old games.
So, while they could have used the IP to make a good game they might now be considering abandoning it after the critical backlash and poor sales.