I need some info on Cryptomining not to get into it more for personal reason than anything else any help given is appreciated.

I wanted to know what is the current state of GPU related crypto currency mining and if it's going to crash soon, because it looks like the whole HD7970 and R9 390 thing is happening where GPU's are skyrocketing in price and then later on people will start selling them at Ebay at about a quarter of their original price to try make some lost cash, and I don't want to miss out on the opportunity to get an RX 470 or 480 for pennies or hell even a 1080.