In my view, this site is strong evidence for the thesis that demand for GPUs will plummet, here's why:
1) If we tweak your link to sort by Market Cap, we can see the next biggest coin to mine after ETH is has only 1% of ETH's market cap https://shorturl.at/lxLS5
2) These smaller coins do not have the capability to automatically or naturally grow bigger market caps, trading volumes, and buy-side demand just because ETH switches to PoS. Mining profitability ultimately comes from a coin's buy-side demand, which is proportional to many things-- fame, developer activity, etc.-- and none of the PoW chains in that list are anywhere remotely close to "breaking out" and growing proportionally with Ethereum, or, say, Solana. How do I know this? Well, I'm an insider that focuses all of his time on ethereum and web3, you'll have to take my word for it :)