Eth miners can still mine ETH after the update it's just that the reward will be lower than what they are today but still ETH mining may remain the favourite even after the update, ETH PoW algorithm isn't going no where

I think they will still mine eth classic etc. even others that will start depending on what’s the next best mineable coin in terms of power/hash/profit/roi ratio when everything flows over to eth 2.0 PoS. New machines will come out and they will be able to mine algos like ravencoin etc. I think. There is going to be an gpu shortage for quite some time now I am guessing few years.