RadeonSI has supported OpenGL 3.3 since last month while now the R600 Gallium3D patches for this R600 (HD 2000) through Northern Islands / Cayman (HD 6000 series) graphics processor driver have landed OpenGL 3.3 compliance.
After the RadeonSI OpenGL 3.3 support was merged, David Airlie at Red Hat published Evergreen Geometry Shaders support as one of the last remaining GL 3.3 features needed to be accomplished for this older open-source AMD driver and then followed-up with the R600/R700 series patches.
This afternoon hitting mainline Mesa was the Evergreen GS support, GLSL 3.30 support, R600/R700 series support, VS output layer support, and other changes to ultimately make this R600 Gallium3D driver now in full compliance with OpenGL 3.3.
With this work accomplished and the Nouveau support also near complete, OpenGL 3 can be crossed out but much of OpenGL 4 remains within Mesa for these drivers plus core Mesa and the Intel driver. At least now for the next Mesa release ahead (likely to be called Mesa 10.1) we now have OpenGL 3.3 support in good standing across all the open-source desktop GL drivers.
Do you think OpenGL 4.0 support will be accomplished this year across Intel / Radeon / Nouveau drivers on Linux? Let us know in the forums. For now if you need up to OpenGL 4.3 support on Linux the only option is using either the closed-source AMD Catalyst or NVIDIA binary graphics drivers.