I've talked with the Microsoft people last month, and Kohji is right, right now they plan on only releasing DX10 for Vista and it will only run on DX10 hardware (which hasn't been released yet either). Since very few of our clients own Vista, we are not porting at this time.

Given that every other thing Microsoft has done has become the industry standard over time, we will most likely end up support DX10. But there isn't a rush since it will be some time (years?) before people will have the hardware to run it.