For handling 2D acceleration when using XWayland for running legacy X11 applications, the plan has been to use the GLAMOR library for 2D over OpenGL. By using GLAMOR, no modifications need to be made to the existing hardware DDX drivers nor any other specialized support since it will simply be piped over OpenGL.
Back in April was when initial XWayland support was added to the mainline X.Org Server as a feature of the upcoming X.Org Server 1.16 release, which is due out in July. Besides that, DRI3 XWayland patches have been floating around since January. It was just a matter of time that today's XWayland improvements made it into the X.Org Server.
The XWayland work was authored by Kristian Høgsberg and reviewed by Axel Davy and Keith Packard. The changes depend upon Mesa 10.2+ for GBM changes. Today's work can be found via this Git commit.
Overall, Wayland support is looking good this year with X.Org Server 1.16 due next month with its mainline XWayland and GLAMOR support, the open-source drivers continuing to improve, and GNOME 3.14 due out in September with proper Wayland support. There's also the upcoming Enlightenment E19 release where there's the new Wayland compositor code.