Well all we can hope for is Polaris 10 turns out better than expected, and forces Nvidia to lower the prices.
If P10XT is faster than the 1070 and £350, the 1080 will look decidedly silly around £600.
Unlikely, I think. My reading is that AMD's approach this time around is NOT to lead in with high-end guns-blazing GPUs, but to begin with very good value mid-range, try to kick Nvidia about in this lucrative section, and then work up with increasingly more powerful cards from there, with Vega and then Navi. It's an interesting strategy that I think could net AMD a lot of marketshare.
But it wont do much to immediately bring down the price of a 1080.
Maybe at the end of the year if they get Vega out by then (I don't think they will but could be wrong).