The next Mesa release will likely be out before the end of November and should contain OpenGL 3.2/3.3 support thus it will be called Mesa 10.0 rather than Mesa 9.3.
Ian Romanick gave a current look at the Mesa code-base this week at XDC2013, complementing the twenty year history of Mesa
. It shouldn't be too much of a surprise, but the Intel developers are hoping by their next Mesa release they will have full OpenGL 3.2 and 3.3 support and thus bump the major Mesa version number to 10.0. It's been talked about before and just confirmed this week by Romanick at the conference.
This Mesa 10.0 release will also be the project's first under their new three-month release cycle over a six month period. Mesa 10.1 is likely to then come next February, but don't expect OpenGL 4.0 support as still a lot of GL4 extensions are to be implemented in Mesa. The Intel developers are also obviously just focusing upon their own driver's support and core Mesa over all of the various Gallium3D drivers.
More details on the current state of Mesa and the GL3/GL4 TODO list items can be found via the PDF slides
and embedded video below from XDC2013.