Apparently Ubuntu 13.04 will use GNOME 3.6. Fallback mode will disappear in
GNOME 3.8, so this will probably affect Trisquel 7.0.
I don't know what Ruben's vision for Trisquel is, so I suppose it depends on
that. Because of LLVMpipe, Ruben might consider GNOME Shell as a replacement
for Fallback mode. But if he wants to stick with the Trisquel theme then
Trisquel might have to go elsewhere.
I've never used LXDE before, but I've seen screenshots of Trisquel Mini and
they look good! I've used GNOME 2 and Xfce, so either of those (MATE for
GNOME 2, of course) would be okay for me as well.