I crunched some numbers on the profit of GTX 1070, 1070ti and 1080 average hash rate at a price of $0.093 watt.

At each graphics cards average hash rate given the possibility of BTC dropping to $1000, the GTX 1080 and 1080ti are the only cards that will turn a profit at .093 cents per watt. They will return about $0.11 profit after the cost $0.29 to run.

A GTX 1080 cost $550+ that doesnt include the other hardware needed to run the GPU. That means it will take over 5000 days to get your ROI, return on investment.

TLDR: My hypothesis based on this observation is, if BTC drops below $1000 threshold Alt coin mining will become nothing more than a hobby and most Alt coin markets will die. Leaving mostly Proof of Stake Alt coins. These are interesting times.