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.
Even if true that would be horrible. 5970 are available used for $300. Paying double for negligible improvement per watt and 33% less performance sound like crap to me.
Given the rise of FPGA if not in 2012 then certainly in 2013/2014 dumping that kind of coin on a lackluster gain in performance and hopes of better kernel optimization seems like a fools errand to me.