Like the Evergreen GLSL 1.30 switching, this isn't happening due to some exciting commit happening today or in recent days, but rather everything has fallen into place and things have been confirmed by developers as working and (hopefully) not causing regressions compared to GL Shading Language 1.30. Previously the GLSL 1.30 support was accessible for these Radeon product families by setting the R600_GLSL130 environment variable.
As written in yesterday's posting, "Outside of the Radeon world, the Intel Mesa DRI driver with Sandy Bridge and Ivy Bridge hardware indicates GL Shading Language 1.30 compliance (that's where Mesa lost its GLSL 1.30 virginity in late 2011). The Nouveau NVC0 "Fermi" hardware also advertises GLSL 1.30 support while the other generations remain at 1.20. Gallium3D Softpipe/LLVMpipe has also been chopping towards GL3/GLSL1.30."
As written by David Airlie in one commit this morning, "r600: enable glsl 1.30 on r700 I've done a piglit run on rv740 and confirmed no regressions. We don't get GL3 on r700 due to transform feedback being busted still."
And then in another commit by Airlie, "r600g: enable GLSL 1.30 for r600 class Full piglit run on my rv610 with no regressions. This only leaves cayman, however my cayman is resisting my attempt to get through a full piglit run."
So while the GLSL 1.30 support is now on-by-default for R600/R700 class hardware, OpenGL 3.0 still isn't the advertised GL version due to missing the transform feedback. There's also not yet GLSL 1.30 as the default for the latest Radeon HD 6000 "Northern Islands" graphics card. The far-from-complete RadeonSI Gallium3D driver for the new Radeon HD 7000 series is also not yet ready for the GL3 age.
Getting closer to GL3/GL4 is good considering it's the R600 and R700 series that is soon getting dropped from the AMD Catalyst driver. The proprietary Catalyst driver meanwhile has quickly supported the latest OpenGL / GLSL specifications following their ratification by the Khronos Group for each generation of Radeon hardware (by the way, there's also a hint of something else coming). The Phoronix Test Suite will now also better illustrate these GL differences.