Today's news shouldn't come as a surprise since I mentioned earlier this month that Radeon user-space mode-setting would be dropped. Radeon KMS has been stable for years now on Linux, new ATI/AMD hardware is only being enabled along the KMS code-paths, the UMS paths are rarely being tested these days, and it's just a lot of old code that can be stripped away.
For the limited open-source Radeon driver development team, this is a big win. The only ones losing out in this situation are those users of Solaris and BSD where there is incomplete kernel mode-setting ports to their kernels. These users will need to stick to the 6.14.x driver series or get onto providing proper Linux-compatible KMS implementations.
The current user-space mode-setting code will be branched in Git should anyone care to take over maintenance on the 6.xx.x series. Meanwhile the KMS-only code will be found in Git master and the open-source Radeon developers will be developing this new code towards an xf86-video-ati 7.0.0 release.
With this xf86-video-ati 6.14.6 release is just two small fixes (including a small UMS fix for fixing CRTC DPMS state checking) and bumping the libdrm requirement to 2.4.36 for KMS support.
The release announcement for this last UMS release can be found on the mailing list. Radeon is the last of the three main open-source drivers (with Intel and Nouveau being the other two) to still support user-space mode-setting.