To give you an idea how big of an impact this is to miners, my 5700 XT went from making $1.2 / hour (mining Ethereum) to $0.15 / hour (mining Ethereum Classic) Eth classic seems to be currently the most profitable coin to mine and it is barely worth the electricity cost.
The people with actual mining rigs with multiple GPU's will either sell their stuff or start renting them for services like vast.ai. I assume most will end up selling because of the cost of getting a server-grade Motherboard/CPU + lots of RAM isn't exactly cheap and the effort required to set everything up is much higher.
Hm, I went on coinmarketcap.com and filtered by PoW, and it shows Bitcoin (of course) and Dogecoin as being PoW with higher market cap. Next three are Litecoin, Monero, and Bitcoin Cash.
The last one I don't expect to work, because mining is about as profitable as Bitcoin, since both use the same algorithm, and the best relative profitability fluctuates between them, and they're both dominated by ASICs. But Monero deliberately avoids ASIC dominance.
The people with actual mining rigs with multiple GPU's will either sell their stuff or start renting them for services like vast.ai. I assume most will end up selling because of the cost of getting a server-grade Motherboard/CPU + lots of RAM isn't exactly cheap and the effort required to set everything up is much higher.