Too many flames in these weekly Wayland discussions and not enough facts (or maybe the facts are downmodded; I've gotten to the point where if I look at a wayland article, I don't read all of the comments).
So, I just spent 5 or 10 minutes skimming the Wayland FAQ and architecture diagram.
For comparison, when running X, you might have an ordinary window manager or you might have a compositing window manager. The Wayland model is that it *is* a compositor that provides both window manager functions and some of the functionality of an X server.
Intentionally misstating things rather badly, it sounds like the reason Wayland doesn't support remote displays is because it also doesn't support local displays! More accurately, wayland supports local displays (of course), but unlike X11 provides no way to render to them. Wayland doesn't do rendering; it apparently "just" knows how to swap video buffers to a display device and coordinate buffers between multiple clients.
I'm thinking that, for example, if you want to write a graphical app, you might target OpenGL or cario and then expect your code to work in both Unix (with X) and on Windows (without X). With Unix/X, I'd expect an opengl library that handed X primitives to the X server. With Wayland, you'd apparently have an opengl library that rendered to a buffer and then handed the buffer off to the Wayland compositor.
So, Wayland isn't doing some of the things we'd expect an X server to do. Wayland is never working with drawing primitives. It seems obvious that you'd never be able to run apps that use the old X toolkit libraries against Wayland without an X server in the picture. And, the FAQ admits this and notes that you'll need an X server in addition to Wayland for the foreseeable future.
However, as others have noted, an obvious question is how efficiently a "native" Wayland app could be displayed remotely. If the app and its libraries are rendering graphics primitives into display buffers, it seems obvious that low level primitive operations are lost by the time wayland gets the buffers, so you now have to be able to efficiently transmit bitmap deltas. Queue arguments re whether drawing primitives are more efficient or bitmaps are more efficient... OTOH, it seems unlikely that apps would include their own rendering code instead of using as library. So, we can hope that the libraries offer both wayland and X backends, I guess.
Not an X server developer nor a Wayland developer. I'm sure I garbled things somewhat, but perhaps someone could clarify the mistakes and help take a portion of the FUD out of the weekly Wayland discussions.