It's been long enough and all it does is cause confusion, perhaps consider cleaning up gnome-panel too.
I think we should just merge gnome3 and gnome, personally. I think the gnome tag should cover whatever is the latest version number of GNOME (with, say, gnome2 remaining separate in case users have questions specific to the older version of GNOME pre-11.10 releases use). When GNOME 4 comes along, gnome could then cover that and gnome3 would once again be its own tag, and so on.
I'm hesitant to accept the idea that gnome-shell should also be merged into gnome. On the one hand, GNOME Shell is intended by the GNOME project to be the official desktop shell for the GNOME desktop environment, so it would make sense that "GNOME" could refer to either.
However, GNOME also includes more than just the shell, as Unity, GNOME Classic, Pantheon and Cinnamon demonstrate. We could have questions come up which are about the underlying GNOME 3 system itself, and not GNOME Shell or whatever other shell is running on top of it. As such, I think we should recognize that the DE and shell are sufficiently different topics that we keep their tags separate, as well.