I know one thing, with hbm2 there not going to be cheap.
As I have said before, they are going to have to be. No one in their right mind is going to pay 1080 prices for an unproven card that performs similarly but chews more power and runs hotter. AMD also have to give an incentive for you to abandon the established market leader and take a chance on their products. The only real way to do that is to come in with either disruptive performance, or disruptive price (or both like Ryzen!). Everything is pointing to the performance not being what we hoped. Which only leaves pricing.
AMD's saving grace is the mining craze, meaning they might actually launch at a much higher RRP than they had intended, while still undercutting the competition due to the currently inflated 1070 and 1080 pricing. Good news for them, bad news for us.
If they do launch at >1080 pricing then they are going to seriously struggle to shift them... well unless the miners snap them all up...