> Which is *designed* to be capable of doing everything X can do.
This sentence isn't very good..
At a high level it is somewhat true, as Wayland is a part of the GUI frameworks and the GUIs won't really change in the end, but Wayland is very different from X, two examples (there are more):
1) Wayland clients don't know where their window are displayed on a screen, X clients do.
2) with X you can send a glyph cache to the remote X server and use this to display efficiently text, with Wayland (alone) you can't do this, you're supposed to render the text locally then send a big image of the result to the server.