Did anyone of you play around with Budgie Desktop yet?
It's based on GTK3 and it's code is on github.
Dependencies:
•libpulse
•libpulse-mainloop-glib
•GTK3 (>= 3.10.1)
•upower-glib (>= 0.9.20)
•libgnome-menu (>= 3.10.1)
•libwnck (>= 3.4.7)
•libmutter (>= 3.10.1)
•GLib (>= 2.38.0)
•gee-0.8 (not gee-1.0!)
•libpeas-1.0
•valac
There is also a package in AUR.
Maybe it could ease the transition to Wayland in the future...