>> GPU may allow creating a cross-platform compute stack That was the intention of OpenCL.
except writing in opencl is a dogshit experience compared to cuda. khronos is incapable of producing an API that's even remotely pleasant to use, vulkan suffers from the same thing. it is one of the worst "design by committee" groups.
OpenCL's API is terrible to use and even if you know all of it's kinks there is much more boilerplate which turns a small script into a tangled mess.