Distributed parallel rendering in Gaming or VR rendering
You are essentially correct in assuming that it is technically feasible to distribute the rendering computation workload. It is, essentially, a computation workload like any other; possibly even better-suited for parallelization due to its very nature: many similarly structured units running the same code path (i.e. vertices, pixels).

What you are forgetting, however, is latency. Having all the render power in the world is useless if the image does not arrive to the HMD fast enough not to cause discomfort to the user. Here is an article that explains the importance of motion-to-photon latency:

http://www.chioka.in/what-is-motion-to-photon-latency/