MS will never drop support for PC gaming.
If DX11 delivers, it would actually drive sales of Windows 7 among the PC gaming niche. Odds are good MS learned their lesson from the DX10/Vista debacle and this generation will see a smoother, more beneficial transition.
DX11 will also be tied to VGA cards as well. MS wants VGA card manufacturers to continue aggressive support of Windows, preferably Windows 7. And vice versa, VGA card manufacturers want MS to provide reasons (ie DX11) for consumers to upgrade video cards.
The decision was most likely partially driven by the acknowledgment that console exclusives can move 360s, but also by the fact that a staggered release (assuming a PC port ever surfaces) could ultimately yield greater margins through the elimination of the bulk of piracy.
So in the case of Alan Wake, the only losers in this deal are the PC gamers. And to a lesser extent, those who have a 360, but were planning on buying it on PC to run higher resolutions and frame rates (probably not an issue for what looks to be slow moving game) with additional effects.









