At least for now
According to our sources, the Radeon HD 7970 is about 30 percent faster in 3DMark when compared to the Radeon HD 6970. These are early performance benchmarks made with the first "usable" driver.
According to the whispers that we are hearing right now, Radeon HD 7970 should end up about 30 percent faster than the HD 6970. These are 3DMark early performance numbers probably done with the 12.1 RC driver that was, at least according to our info, released two days ago. This should put the HD 7970 somewhere around Radeon HD 6990.
We are also hearing that the HD 7970 does even better in game benchmarks and we hope that we'll have more details regarding those pretty soon, as after all, game benchmarks are the ones that really matters when it comes to performance of graphics cards. We still don't know if there will be another driver before first reviews hit the net, but AMD usually holds the final driver as long as it can to control the performance leaks.
Some slides have leaked over at Donanimhaber showing that Tahiti might do a lot better when it comes to tesselation, but once again we are talking about AMD slides so we tend to tread lightly there.
In any case, we'll know for sure on 22nd of December.