XFCE is written in GTK, the same as GNOME. It uses fewer resources, but it
is not the most lightweight DE. I am not sure how long GNOME 2 will be
available once GNOME 3 comes out on a distro like Ubuntu that uses the
latest and greatest. On a distro like Debian stable which is two years
behind Ubuntu it will be available a lot longer. The same could be said for
LTS Ubuntu. I don't see development of GNOME 2 going anywhere because it is
unlikely that GNOME will work against itself and undercut adoption of GNOME
3.