There's an incredible number of improvements to be found in Mesa 7.11 that have built up over the past six months. There's support for new hardware, performance optimizations, new OpenGL extensions, Gallium3D advancements, hardware driver improvements, and a lot more. When the release nears there will be a proper Phoronix overview as there is simply so many improvements that have went into Mesa for this 7.11 release.
Ian's plans for doing the 7.11 release have it for branching on the 24th of June, the first release candidate on the 8th of July, a second release candidate one week later, and the Mesa 7.11 final release on the 22nd of July.
Romanick also comments that a six-month release cadence for Mesa seems to work out well so the next Mesa 7.12 (or Mesa 8.0) release will not occur until January of 2012. The plans for Mesa 8.0 are to bump the major version number when OpenGL 3.0 support is in place.
The Mesa 7.11 release plans can be found on the mailing list.