To clarify, my statement was made with respect to the technology lead. And there is no doubt ATI will release their DX11 chips first, and in the months that NVIDIA is still struggling to get the GT300s out in the marketplace, ATI will have the tech lead over NVIDIA. They may even force NVIDIA to lower prices for DX10 chips by releasing DX11 chips at competitive. for example, given the option of a next-generation DX11 chip that equals the performance of, say, a GTX 275, almost anyone (except maybe those using 3D Vision or doing CUDA programming using hte GPU) will end up going for the ATI option. This will force NVIDIA on the backfoot as they'll have to slash prices on their cards to remain competitive. currently its ATI that's on the back foot.
and as a result of ATI going to market with DX11 first, all the early adopters will thus have no choice but to go to ATI for DX11 chips.... or wait. but waiting is not 'early adopting'
ATI claims it will release its high-end RV870 based GPU at around the time DX11/win7 launch. NVIDIA's GT300 is not expected to be distributed in volume until March 2010, which is quite a bit of a ways off.