Support for the R500/600 GPUs later came to the xf86-video-ati X.Org driver via implementing AtomBIOS rather than the xf86-video-radeonhd driver's hard-coded setup. AtomBIOS was also used later within the Radeon kernel mode-setting driver for the Linux kernel. It is the xf86-video-ati DDX and Radeon KMS driver that has succeeded the RadeonHD driver with its support now for all GPUs from the R100 series through the most recent Radeon HD 5000 "Evergreen" series and soon enough will be the AMD Radeon HD 6000 series support once launched.
While the RadeonHD driver may no longer be worked on nor is there any communication going back and forth between AMD and Novell (well, soon to be VMware) in terms of open-source driver development, according to our initial 2010 Linux Graphics Survey results, there still are a number of users continuing to use this open-source ATI driver.
On a related note, congratulations to John Bridgman of AMD on becoming the number one contributor to the Phoronix Forums with more than 5,100 posts since the launch of the RadeonHD driver three years ago.