nVidia has some very powerful servers with lots of Kepler boards and they are great for professional rendering for movie studios, who can afford to pay $20K+ for these things to improve productivity.
I don't think MS have GPUs in their cloud. Xeon CPU's designed for cloud don't even have embedded graphics. Even though one or two cores on a Xeon server may have quadruple the power of the Xbox One CPU, it's actually not enough to draw much graphics. The XB1 can render far more graphics on it's own.
We shall see. There are a few things that can be done, but not very impactful IMO, and take a lot of developer effort. I mean, I'm a graphics developer. If you asked me to come up with any ideas for using the cloud for graphics I could give you some, but if you asked me if I think it's a good idea I would say no way.
Devs will use the cloud for what is a good fit, not try to do something weird which would break the game if you had spotty connectivity or an offline user.
You do know that you do not have to have a GPU to render graphics. Also a lot of new graphical features can be easily done using CPU compute. Using thousands of CPUs in the cloud to perform those calculations is called cloud compute. Also Intel Xeon chips actually do perform graphics calculations and from a little research their E3-1200v3 chip is built off theire Haswell design. Even AMD offers graphics processing with their Server Opteron chips. Its a misconception to believe that Nvidia has the only option or that their solution is the only one that can be leverage.
The thing is you are limiting your thinking to what is done today. Thats actually being very narrow in your perception. New techniques are being developed every moment and there probably will be plenty developed using cloud compute. I see a lot of pontential in this space because I have seen throughout my years how fast cloud based tech has improved. Now that companies like Intel, AMD, Nvidia and MS are leveraging their skills in this area mean we will start to see a lot of innovative ways cloud compute can expan this space.