well that's bad, because right now a 390 can do the same with the same wattage, now imagines what a 490 can do
so i think if the new gpu will not be optimized in some way they will be out of the cryptoscene altogether
It's not unthinkable that AMD is going the same way with their architecture. You already see that in their GCN1.2 line. Narrower buses, delta compression, all to save power. I wouldn't be surprised if 490 also sticks in the 20-25 range for ETH.
With 2MB page size support we may see performance up to full bandwidth utilization. But that's pure speculation.
Do you have a chance to use the 1080/70 and optimise the Ethereum miner? I hope it will be faster.