For Fedora 21 it will most likely ship with the GNOME 3.14 desktop environment that's now just in early stages of development and should improve Mutter-Wayland and other non-X11 code quite a bit more over the next few months. Many of the involved GNOME developers are Red Hat developers -- including some working on Wayland/X.Org -- and now they're trying to make more Wayland inroads for the Fedora 21 release due out before the end of the year.
The Wayland feature proposal for Fedora 21 was just submitted for review and evaluation by the Fedora Engineering and Steering Committee.
The Wayland feature proposal for Fedora 21 is documented at length via the Fedora Project Wiki. X.Org Server support is expected to still stick-around for unsupported hardware/driver combinations and now that X.Org Server 1.16 has integrated XWayland support. Besides GNOME 3.14 and X.Org Server 1.16, on the software version side for Fedora 21 will also likely be Wayland 1.6.
GNOME is being ported to Wayland. In particular GNOME shell is changed to run as a Wayland compositor instead of an X11 compositor. Other components of GNOME that currently talk directly to the X server, such as gnome-settings-daemon or gnome-control-center, will be ported to corresponding Wayland interfaces. Many GTK+ applications will just work, using the existing Wayland backend. Applications that make use of X-specific APIs will be supported with the xwayland X server, which is started on demand. gdm will be changed to support both Wayland-based sessions and X-based sessions.
This change is targeted at F21. For F20, we aim for having an experimental GNOME shell Wayland compositor available, without necessarily having all the surrounding desktop infrastructure ported. To avoid destabilizing the X compositor, mutter will ship two separate libraries, and gnome-shell will ship two binaries that will link against them. Concretely, we plan to have a separate mutter-wayland package.