AMD cards don't support CUDA.
That's correct, AMD has announced that they support OpenCL as the GPGPU language. And OpenCL is an open standard as opposed to CUDA (NVidia proprietary).
which one could be running wesnoth in the future?
Forget the "future". Maemo already runs Wesnoth, and quite well at that.
"The Avis WIZARD decides if you get to drive a car. Your head won't touch the pillow of a Sheraton unless their computer says it's okay." -- Arthur Miller