ATI's R520 will finally come by early October after three tape-outs and being delayed for a full quarter because the yields weren't good enough. The chips worked fine but ATI claims it wasn't able to clock them high enough, according to the Inquirer.
In the meantime another separate team at ATI has finished the R580 and successfully taped it out a couples of week ago. This chip only needed to be taped out once while the R520 which needed three tape outs before ATI was satisfied.
The R580 is expected to have some more pipelines, some architectural upgrades and a higher clockspeed. Launch date is unknown but it will probably take until Christmas or later before this chip will arrive in retail stores.