If only there was a uniform, unchanging, future proof API for DirectX- that would make me want to use it. I like Direct3D9, its fun the play with. But I'd rather use OpenGL to create stuff. Its simple, elegant, widely supported, and futureproof.
DirectX is future proof unless I'm missing some aspect of it. Blitz3D still runs on DirectX 9 systems, correct? You just specify which version of DirectX that you want to compile/link against and your code never needs to change.