Yes they will. Windows always provides backwards compatability with the recent generation(s) of computer hardware and operating systems to ensure a "smooth transition"(I.E., so customers would buy it. No wants to find out that all their favorite programs all of sudden doesn't work any longer.). As far as DX10 and DX9, I've read on Microsoft's DirectX documentation that all series of DirectX maintain backwards compatability so it should remain functional(Most, if not all, recent generations of popular "whatever" software/drivers/technology from microsoft has backwards compatibility for smooth user migration and minimal customer headaches.) . Now for if they'll change that in the future... I wouldn't know. I'd have my doubts, but they may do something when "vienna" rolls about; Vista is apart of the transitioning from XP to 'Project Vienna', which are supposedly fundamentally different.