I envisioned just copies of the f15 change sets being built against f14 and published into an f14 repo. This could be done by somebody not necessarily being distracted with upstream and f15 tasks.
I have an up to date legacy-build branch of mutter and gnome-shell that I will make public once I fix the performance problems with the new statusIconDispatcher. My branches carry pretty much all the patches minus the GSettings and updater Introspection stuff. I have tested it and it builds and runs on F13.
If people want to test Gnome-Shell on F14 this will be available for them.
-Jon