Ian Romanick of Intel announced tonight Mesa 10.1 RC1. The 10.1 RC1 message is very short but can be found on the Mesa-dev mailing list.
Those readers that haven't followed our near-daily coverage of Mesa Git activities leading up to Mesa 10.1 on Phoronix can see these Git details for some information on the changes. There's also the dozens of Phoronix articles covering the various driver changes, especially OpenGL 3.3 for non-Intel drivers. In the next few days I also intend to write a summary on the new features and performance improvements that have been queued up for Mesa 10.1.
If all goes according to plan the Mesa 10.1 official release will happen on 28 February, but already there's noteworthy work for Mesa 10.2.