I've been wanting to buy a 1060 6gb or a rx 580 for a while now and the prices are insane! When are they expected to drop?
No one really knows for sure. It could be a few more months, or even as long as the rest of this year.
No way to accurately predict. If you can't or don't want to wait to buy, I recommend setting up an auto notification through EVGA's website or http://www.nowinstock.net/computers/videocards/nvidia/gtx1060/, wherever you can find cheaper. I've been stalking EVGA since that's the brand I want, and since you can buy direct from them you avoid any additional markup from another merchant. Another thing to consider as well, even when the price gouging stops and supply meets demand, expect to pay a little more than what MSRP used to be due to rising memory costs.
On those cards for new probably never.
AMD is ramping up production for Vega and the Vega Polaris replacement.
NVidia is supposedly launching Volta soon but could also easily refresh Pascal with AMD only just catching up in the high end.
Both of those cards are over a year old at this point and had things gone as expected would already be off the market.