The Radeon DRM driver changes for the Radeon HD 7000 series of graphics processors was merged into the Linux 3.4 kernel. On the Gallium3D side for the user-space OpenGL driver, that was published last week and living in a separate Mesa branch. Now though that's been changed as today Tom Stellard pushed it to mainline Mesa Git master.
This new Gallium3D driver for the latest HD 7000 generation of AMD GPUs, is still far from being complete or close to on-par with the earlier Radeon Gallium3D drivers (R600g and R300g). In the commit message, Tom Stellard mentions that just "egltri" is starting to work. Due to Southern Islands / GCN being a radically new architecture, the R600g driver wasn't extended but there's much work left to bring this new open-source enablement code up to speed.
As shown with the commit, this new "RadeonSI" driver amounts to 66,000 lines of new code. However, also included as part of this commit is the R600 LLVM back-end as it's been a slow process getting it pushed into upstream LLVM so for now at least it's being included externally within Mesa.
The AMD developers are continuing to plan on using Gallium3D for accelerating X.Org/2D. Right now there's the Xorg state tracker and XA state tracker for doing 2D X.Org acceleration with a replacement and generic DDX driver, but it's not clear at the moment if they're going to use it. According to comments made by AMD's John Bridgman in this forum thread, they're still deciding about how to do the X acceleration over Gallium3D.
For now any Linux desktop users with an AMD Radeon HD 7000 series graphics card are better off using the Catalyst Linux driver until the RadeonSI support matures. The Phoronix review looking at the Southern Islands support with Catalyst can be found in the AMD Radeon HD 7950 review and the follow-up article.