Hello Linux Geeksters. There were discussions on whether to use Gnome 3.10 or Gnome 3.8, as default on Ubuntu 14.04 Gnome. Since Ubuntu 14.04 will be a LTS (long term supported) release, the latest versions of the Gnome Desktop, Gnome 3.10 may produce instability.
Now, Sebastien Bacher, one of the Canonical developers has announced in the mailing lists that they have started the migration of Gnome 3.10 and GTK+3.10, on Ubuntu 14.04 Trusty Tahr.
So the Gnome flavour of Ubuntu 14.04 Trusty Tahr will be using GNOME 3.10 as default.
Using GNOME 3.8 on Ubuntu 14.04 LTS may offer stability, but will be unfair for the Gnome users, who want to have the latest GNOME apps on their system, or at least, not ones from two cycles behind. Many other important Linux systems, like Fedora and Mageia use or will be using Gnome 3.10 as the default desktop environment, on their Gnome flavours.
As a reminder, Ubuntu 14.04 LTS will be released on the 17th of April, 2014 and will be a long term support version. The users will be able to test the first alpha version of Ubuntu 14.04 LTS on the 19th of December, 2013. More information can be found here.