Actually they didn't. The chart is right. It is just that nvidia used the 670 as the 680 because the kepler was performing so well against AMD. We haven't even seen the 680 in my opinion.
so we don't know the actual stats until the company launches keplers?
That has always been the case with any new generation of products. The only thing you can do without a released product is make an educated guess nothing more. The product name that should fit in those spots are the 670 and 660 how will they be priced and how will they perform is anyones guess. All we know is they should perform similar and based on the power usage of the 680. They will likely use less power at load an more at long idle. Given that the long idle power usage of the 7970 is lower than the 680. Normal idle power usage will likely be similar though. (within a few watts).