I don’t think it’s possible for them to do so, because that would means killing the gaming aspect of Windows. GPU on cloud is stupidly overpriced and expensive, just look at Standard_NV6 for an example, it easily cost $10,000/yr according to this (Just look for anything that have “N” in it’s name for GPU enabled VM and they are all expensive.)
If they try to ban everyone from being allowed to use their own computer hardware, I really doubt people would stay on Windows, they most likely would be in the 5 stages of griefs and then contemplate on switching to either Linux or Mac OSX.