You might be using the wrong terminology here.
1. Certainly SGDK2 is compatible with DirectX 10. If you have DirectX 10 installed, I don't think that prevents you from running SGDK2 on Manged DirectX 9 on the same system.
2. Vista may not use DirectX 9 or OpenGL, but that doesn't mean you can't run DirectX 9 and OpenGL on a Vista system. Just because the OS doesn't use it doesn't mean applications running on the OS can't use it.
I don't suspect those are the questions you meant to ask, but I think those are the correct answers. One thing I can tell you is that SGDK2 does run on Vista, which might answer your real question. Another thing I can tell you is I don't intend to do any more new DirectX-based development on SGDK2. All new development for SGDK2 will probably be in OpenGL. I don't think that will be limiting. On the contrary, I think that will enable SGDK2 to expand to more platforms than before.