Edge says that Ubisoft Montreal is working on the next gen games based on what Microsoft intends the next Xbox to be and they should receive official dev kits by Christmas. Edge says the next Xbox should be ready by Holiday 2012.
Also one Sony first party studio has stopped working on the PS3 and gearing up for next gen.
There have been strong rumors going around that Microsoft will announce the next Xbox at CES (January) and my personal opinion is that it makes sense. Imagine Halo 4 becoming the Twilight Princess for Microsoft.