Michel Dänzer posted a set of sixteen Mesa patches plus two LLVM patches onto the mailing list this morning. "This patch series adds GLSL 1.50 geometry shader support and thus OpenGL 3.3 support to the radeonsi driver."
With these patches all of the OpenGL and GL Shading Language functionality is met to enable to OpenGL 3.3. This major milestone is coming several months after Intel added OpenGL 3.3 support to core Mesa and their own hardware driver for Ivy Bridge / Bay Trail / Haswell hardware. Still to join the GL3.3 party though is the open-source Nouveau (NVIDIA) graphics driver. It will also be another big leap and quite some time before OpenGL 4.x support is officially met for the Radeon -- both RadeonSI and R600g -- Gallium3D drivers.
The patches providing GL 3.3 / GLSL 1.50 for RadeonSI Gallium3D, the hardware driver that supports the Radeon HD 7000 series graphics cards and newer, can be found on Mesa-dev. For end-users you will need what's going to be released as likely Mesa 10.1 (it doesn't look like OpenGL 4.0 will be met in time for core Mesa to cause the version to bump to Mesa 11.0) but then as there's also LLVM compiler patches to the AMD GPU back-end it will require LLVM 3.5 too. LLVM 3.5 isn't going to be officially released until like June or July while the next Mesa release should be out in March or April.
In case you missed it, new benchmarks this week show RadeonSI Gallium3D OpenGL performance catching up to Catalyst but the proprietary driver still has its advantages. For the older Radeon Gallium3D, it can beat Catalyst in some situations.