According to info from Ocaholic.ch, AMD is still working on an R9 280X version based on an updated Tahiti XTL GPU which should be ready sometime in November and silently replace the R9 280X currently running on the Tahiti XT2 GPU.
AMD apparently plans to do a "running change" which means that there will be no announcements for the new GPU or even a name change for the R9 280X graphics card and the only way to differentiate these cards is to check out the BIOS version. As always, these rumors should be taken with a grain of salt since nothing is carved in stone and AMD can simply use the new GPU to launch a new graphics card under a different name but currently AIB partners have been told that it will be a running change.
According to the same source, Tahiti XTL should have a lower power consumption and thus cooler. Unfortuantely, it is still not clear if there will be any specification changes, higher clocks or changes in the feature set. Eventually someone will spot it when it hits retail/e-tail in November.