It would stand to reason that if per-shader-performance can be maintained on the same levels as with the VLIW hardware, then the 7970 should be 25% faster than a 6970.

With all the improvements GCN makes, I wouldn't be surprised if mining performance could be improved beyond. But I wouldn't be disappointed if it cannot be improved either, as I'm not familiar with the practices required for writing a mining application.

And 7970s can be overclocked a LOT. Though I imagine that could shoot up the wattage as well. Regardless, I'd wait for optimized kernels before believing any benchmark scores.