Preventing the RadeonSI driver from advertising OpenGL 3.0 (or greater) like the R600, Intel, and Nouveau drivers has been its lack of transform feedback support. As described via the OpenGL.org Wiki, "Transform Feedback is the process of capturing Primitives generated by the Vertex Processing step(s), recording data from those primitives into Buffer Objects. This allows one to preserve the post-transform rendering state of an object and resubmit this data multiple times."
Marek Olšák submitted a set of 11 patches to the Mesa-dev list on Tuesday that implements transform feedback for RadeonSI and also enables OpenGL 3.0 support, since it was the last remaining feature.
These 11 patches also depend though on a Radeon GPU LLVM patch, which will end up being released with LLVM 3.4 likely by the end of the year. So if you'll want GL3+ support on RadeonSI, you're going to either need to be pulling the LLVM development tree for the latest support or wait until 2014.