With the latest RadeonSI Git activity this open-source graphics driver that supports the Radeon HD 7000 series graphics processors and newer supports the OpenGL 3.3 specification after being stuck to OpenGL 3.1 on the current Mesa stable release. The hardware is still capable of OpenGL 4.3, but that will be many months before we see official OpenGL 4.x support out of this RadeonSI Gallium3D driver or the older R600 Gallium3D driver.
While this newer Radeon Gallium3D driver now supports OpenGL 3.3, the R600g driver still only supports OpenGL 3.1 but there's a Git branch of Mesa working towards GL 3.3 compliance on this driver that supports the Radeon HD 3000 through Radeon HD 6000 series GPUs.
It was also this week that Nouveau Gallium3D gained OpenGL 3.3 support, the reverse-engineered open-source NVIDIA driver on Linux. This OpenGL 3.3 support covers both the NV50 and NVC0 drivers, or the GeForce 8 series and later.
This next Mesa release supporting OpenGL 3.3 for Radeon and Nouveau hardware should come in the next month or two. Its version will likely be Mesa 10.1 as the major version number is only generally bumped when reaching a new OpenGL version number inside core Mesa. Mesa 10.0 was the last release back in December when the core Mesa code -- along with the Intel open-source driver that generally leads on the OpenGL compliance front -- reached initial OpenGL 3.3 compatibility.
For those curious how the current R600g and RadeonSI drivers are performing, see this week's 25-way open-source GPU comparison featuring hardware from Intel, NVIDIA, and AMD. New benchmarks will come on Phoronix of this latest Mesa code in the next week or two.