It looks like the Raspberry Pi ARM bords give better performance with Wayland and using the Weston compisitor, than the good old X.org server.
From performance reasons, Wayland would replace X.org completelly, soon. The founder of Raspberry Pi, Eben Upton has showed a live performance of Wayland/Weston on RasPi at the LinuxCon event.
In the following weeks, a preview of Raspberry Pi running on Wayland should be released on the newest RasPi ARM bords.
As you may know, many important developers contributed to the development of Wayland, in order to replace the X.org server with it. Gnome will add official support for Wayland in Gnome 3.10 witch will be released in the last week of September 2013 and Fedora 20 should be the first Linux system to be released with Wayland.