Well if people paid taxes for really expensive game skins before ( i haven't heard that they did), i guess nothing would change on that front.
But if not, i am guessing you can opt out from any ski trading activity because online game companies sure as hell aren't going to drive away potential customers that won't be filling kyc or buying and selling skins. They can still buy games and addons even if they are not selling them forward.

It's not like every game will have mandatory marketplace. But sure, people who buy and sell skins, either nfts or not, will be most likely be filling mandatory kyc.