I understand it depends on electricity cost and other "future value" thinking but at what price point of ETH, people plan to stop rig?
Under $200 most will quit or shutoff machines.
Many already have.
That is right. The difficulty is dropping now.
If the difficulty is dropping why I don't see it in my results of Nicehash miner, I had 0.55 mBTC yesterday from a rig with 6 Rx 580 cards and I am still having the same reward daily from the same rig ?
Maybe Nicehash acts a little later and that is why I don't see an increase in rewards value from my miners.
Yep, profitability on Nicehash is based on how much people are willing to pay for your miner, and profitability tends to go up slower than down, especially when difficulty changes are small like what just happened with ETH. Give it some time, it'll likely go up if difficulty doesn't continue going up.