I know patreon and ko-fi links are banned on AO3 but how will / will the archive be updating at all to accommodate for fandoms like Genshin Impact that allow profiting off of fanficition?
Why would it change for Genshin Impact? Jane Austen's work is out of copyright, and you still can't post your ko-fi links on your Jane Austen fic.
The issue isn't that profiting off of fic is illegal. That wasn't always true when AO3 was founded either.
The issue is that AO3 was built to protect a type of fandom that is a gift economy.
If my friend shows up to my dinner party expecting me to let them turn it into a sales pitch for their multilevel marketing garbage, I will be annoyed. They have violated the social contract. They have taken a space I did the lion's share of the work to build and attempted to monetize it in a gross way. Let them host their own dinner party if they want to do that!
Similarly, those of us who gave years of unpaid labor to build an archive where our style of fandom—a not-for-profit kind—could be safe are not interested in that space being warped into etsy or a dealers' room at a convention. If other fans have other styles of fandom, that's fine: they can build other archives for them.
Personally, I find that the introduction of a profit motive turns fic spaces from a place of peers sharing into a place of Audience vs. Content Creators, and I get enough of that hustle culture on every other site, thank you.
AO3's popularity is likely partly due to how much it isn't full of desperate shilling and begging. The fact that there's no incentive to post chapter 1 and paywall the rest is incentive for readers to trust and like AO3.
The legality of Genshin Impact fic is irrelevant. AO3 bans commercial spam because it wants to.