Why is the game industry going to give up one of their major channels of revenue or allow it to be shared between properties or even other companies?
Remember that NFT contracts can be written such that the original issuer can get a piece of secondary sales. That is a new revenue stream for the content owners.
I think that interoperability will not be universal, but maybe you can buy NFL gear on an NFL website and then it happens to also work in the licensed NFL games -- stuff like that. Or Nike negotiates with Fortnite and Roblox and Minecraft so that Nike NFTs that you buy from Nike.com work as avatar customizations in these games. I think this is how it starts -- limited and negotiated interoperability between non-competitors. Maybe it gets to where competitor games have interoperability, but that is definitely not where it starts.
You can't even use items from D&D 3.5e in D&D 5e.
There will not be universal interoperability of functional items across disparate games, and only limited interoperability of functional items within game families/series.