Whether the commands to the virtual device are sent to an open port 8000 or sent encrypted over an ssh link doesn't seem to be particularly important. It's the initial step of being able to connect any GUI to an arbitrary virtual display that is key. True, X with no security and an open port 8000 allows anyone to start an X client on the display with no local account needed, but I haven't seen this in use since the demise of the X terminal (good riddance. anyone want one? I need to clean out my office).
It seems likely that if Wayland compositors support a version of Xnest, then effective networking will work. But it's the initial level of abstraction that is needed.
Saying that X support will continue as long as codes support X is truly begging the question. The problem is the next time serious modifications to a code are made; in most cases, if network support doesn't happen for free, the developers will not bother.