the current release schedule puts Gnome Shell out of bounds for Maverick, but it will be packaged and available from universe
So while the GNOME Shell that leverages Mutter will be available in the Ubuntu Maverick repository (well, it's already available in the 9.10 Karmic and 10.04 Lucid repositories too), it will not be the default until at least Ubuntu 11.04. This should give GNOME Shell developers more time to stabilize the work, X.Org/Mesa developers to further improve the graphics stack, and by then hopefully LLVMpipe will play better with the GNOME Shell for those without hardware 3D/OpenGL acceleration.
During this nearly hour Q&A, Mark Shuttleworth also addresses questions concerning what web browser will be used in Ubuntu 10.10, whether mixing money in open-source communities hurts volunteers, and what is exciting Mark the most about Ubuntu these days. For those that missed it live, the full transcripts from the Q&A can be read on the Ubuntu Wiki.