GNOME 3.0 which is supposed to include the new GNOME Shell as well as GTK 3.0 has been delayed for 6 months to March, 2011.
The decision was taken at the GUADEC conference:
We could release in September and have something working that is okayish, but it's not up to the standards we have.
says Vincent Untz, release team member.
Among the options discussed were the release of GNOME 3.0 with the classic 2.x user interface or to release GNOME 2.32 as a new stable release instead of 3.0 for now - this second option being the decision which everybody seems to agree on.
That means GNOME Shell won't be default in Ubuntu 11.04 so the first Ubuntu version which might get Shell by default is 11.10.
You can read more about it @ http://derstandard.at/
GNOME Shell was voted the second most awaited Linux project of the year by the WebUpd8 readers.