Just to help you here is the article heading: "Radeon HD 6970 is 10 - 20% faster than GTX 480"
In the article he says "When we compare our own GTX 480 results and add 20 percent on top of that it turns that Cayman XT loses to both GTX 570 and especially GTX 580."
Most reviews had the GTX 570 about as fast as the GTX 480.
So can you explain how the HD 6970 can be slower than GTX 570?
Do you believe the HD 6970 is going to be slower than GTX 570?
GTX 480 is 13-15% slower than GTX 570 in Vantage.

Still my guess is that 6970 will be at midle between GTX 570 and GTX 580.
Probably 6950<GTX570<6970< gtx 580.