It won't work like that.
Nvidia managed to rebrand pimped up GTX680 as GTX770 because...well...they are Nvidia. Same pricing model won't work for AMD, considering they've been selling comparable, if not faster cards than the GTX670/GTX680 at much lower price points for a long time and still struggle to shift as high volume in sales as Nvidia. If they are rebranding 7950/7970, they'd have to either a) sell at the current prices with the same spec b) slighting higher than current prices, but with small bump to the steam processor counts. Selling a straight rebrand of 7970 at £300 again simply won't work, and I don't think AMD is stupid enough to not realise that.