The rendering modes modern applications use (SHM and dri2) are already just swapping image buffers around. The applications(the toolkits mostly) are doing all the rendering. So you if you are accessing X11 remotely you are _already_ sending image buffers over the network. Wayland can will be no worse at that and can potentially be much better.
[1] http://xpra.org/
Any Linux VNC server worth its salt already support tunneling RFB over ssh. To take it a step further, you would just need very little display server support for an ssh server to request the framebuffer of an application it opens and send it via RFB or the vnc server to the client.
And I'd imagine Wayland already has some mechanism for other applications to read somethings frames. If it is generic enough, ssh should be able to use that. My only concern is that Wayland would need to be rendering programs but not displaying them locally, and I don't have any understanding of Wayland's internal implementation enough to know if it supports hidden windows like that.
"We think it's going to be better at remoting than X," Stone said, or at least it cannot be worse than X.
That is encouraging. I was worried that they were going to simply drop support for opening remote windows altogether. It looks like they've learned from the behavior of graphical networking outside of X.
As I understand it, it's going to only support forwarding of the whole desktop (like VNC). And this would be a huge functionality regression.