There’s talk on the mozilla.dev.planning that the Mozilla Corporation could be considering creating a new Mozilla-based Desktop Environment (like GNOME or KDE) soon.
“I’m only proposing that we make a desktop environment, the same thing that KDE and Gnome, are. The only reason I mentioned a “Mozilla OS” is because we’d probably also want to release distributions for one of more specific kernels as a whole OS, including with it Firefox, Thunderbird, and any other applications built with the Mozilla platform available then. Currently there are plenty of kernels to put a Mozilla desktop environment on.” – Emery Denuccio
Sounds pretty interesting, really.