Pre merge, Eth constituted more than 94% of GPU mining which by far outstripped all other coins combined in energy consumption. Pretty sure a post merge shift to other coins will tremendously increase the difficulty of these coins to a point of unprofitability. I doubt any of the current alt coins can reach the trading volume and appeal that Eth had for GPU mining that could constitute an impact on GPU pricing and inventory shortages any time soon.
Yeah but miners are moving to other coins now. As i said a few months back, overall this changes nothing, its going to be a carnage of hashrates and difficulty swings on the other coins while miners change from one crypto to the other, for a while, then things will settle down, the next "go to" coin to be mined will be know and it will be bussiness as usual.
The key here is pre-mining before that happens, this is why miners will be mining even at a loss until the dust settles down. For example ive been mining RVN with a half dead RX 570 4GB gpu for a year, the amount of coins that GPU made is way more than what i could make now even if i tried.