Ubuntu Studio has traditionally used the standard GNOME 2.x shell, but going forward, they feel they wouldn't be happy with moving to the GNOME 3.0 Shell or to Canonical's Unity desktop like is found in Ubuntu 11.04. "The team simple feel that Unity and GNOME-Shell do not fit our target audience or intended workflow."
What Ubuntu Studio's development team has done instead is they have decided to re-base their Ubuntu derivative on the Xfce 4.8 desktop. Future releases of Ubuntu Studio will be using the Xfce desktop with a custom user-interface and will use the Avant Window Navigator with this alternative desktop. The announcement was made on the project's mailing list.
For those not concerned about multimedia applications, there is already Xubuntu as another official Ubuntu derivative that ships with the stock Xfce desktop.
Changing out GNOME for Xfce isn't the only major change planned for the Ubuntu Studio 11.10 release, but they are also investigating what to do with PulseAudio and whether it could be tossed out the window. It's not too likely they will be able to do away with PulseAudio completely, but according to this message they will try to at least better integrate JACK with PulseAudio.