For a while it looked like Ubuntu 14.04 would stick to a GNOME 3.8 world, for the GNOME packages it ships in Ubuntu Linux as newer packages are partially held back by Ubuntu dependencies for their Unity desktop. Previously blocking the GNOME 3.10 update in Ubuntu was the GNOME Control Center, which ended up being forked by Canonical until their own Ubuntu System Settings can be developed.
Pushed this morning into trusty-proposed was the GNOME Shell 3.10 package to replace the earlier 3.8 release. GNOME 3.12 is going to be released in March, but that will be too late for the Ubuntu 14.04 LTS release. Other GNOME 3.10 packages have also been pushed recently into the Ubuntu "Trusty" archive.