Actually, once again just nitpicking, but many of the optimizations (tesselation, etc) of DX11 will be supported on DX9-10.1 cards. Shader Model 5 and I think the multi-core GPU support is specific to DX11 hardware.
But you are correct that the game will have to support these enhancements to really take advantage of it. There are a few games that have been delayed to include DX11 support, and since it is just an evolutionary step over DX10, I think strong support will come much quicker than for DX10, which was dreadful.
But all around good points.