The open-source drivers would only work with the ATI RV710/730 GPUs when using an analog D-Sub interface. Novell's Egbert Eich though has committed changes to the RadeonHD driver that should introduce proper mode-setting support for these new ATI GPUs. Changes had to be made to the driver to support DCE 3.2 on these newer graphics cards as well as changes to support AtomBIOS.
AtomBIOS is ATI's video BIOS abstraction layer that is supposed to conceal most of the chip-to-chip differences from the driver, but it wasn't the magical savior this time around. The RadeonHD driver had adopted AtomBIOS usage earlier this year under pressure from AMD in delivering the open-source RV770 support.
PCI IDs for the RV710, RV730, M96, and M98 GPUs were also added to the RadeonHD driver yesterday. If you're interested in checking out this open-source work, use the latest git code available from FreeDesktop.org.
Sadly this support only allows for mode-setting but no video, 2D, or 3D acceleration. AMD has been promising R600 3D documentation for many months now, but so far it hasn't got past their lawyers. AMD and Red Hat developers though have been working internally on adding the R600/700 3D support to Mesa, so once they finally manage to push out some documentation, we should see some code shortly thereafter (or perhaps even before the documentation arrives). Since August they have had open-source RV770 3D support running in their internal code repository.