Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
While most of the Linux desktop talk these days is about Unity, KDE, and GNOME, advancing in a quiet but steadfast manner is Xfce. The next major release of Xfce, version 4.12, is due out in March. It's undecided at this time though whether Xfce 4.12 will use GTK2 or GTK3.
Xfce 4.10 was released in April of this year and uses GTK2 as it's tool-kit rather than the newer GTK3 from GNOME. From the Xfce 4.12 road-map they do have an aim to switch to GTK3 for this next feature release, but it might not happen.