Outside of hobbyist niche uses, sites won't start being hosted IPv6-only. The financialization of IPv4 addresses will simply get worse and be even more pay-to-play than it is now. Amazon raises the price of IPv4 and everyone goes along as a cost of doing business.

If you have a big site and want as broad an access as possible I agree.

But I wouldn't be surpised if we start seeing self-hosted minecraft or factorio servers with ipv6 only.

My prediction is that sites will be half-IPv6 only; backends will be IPv6 and IPv4 traffic will get proxied to IPv6 by CDNs / edge LBs. I think CloudFront for example supports that scenario, avoiding IPv4 costs (in theory).

that may be true, but not being able to access hobbyist sites still feels like "being locked out" of something. My ISP provides /48 IPv6 addresses for free, and I already run a couple sites only on IPv6 - because an IPv4 would cost 20 bucks a month - it's not important enough to me personally to pay that.

Yeah, hobbyist niche sites like these:

https://clintonwhitehouse1.archives.gov/

https://clintonwhitehouse2.archives.gov/

Maybe "think of the children."

There might be a child behind the NAT, thus IPv6 requirement.

With IPv6 privacy extensions it's impossible to tell which device you're talking to inside of a /64. You'd need to do something silly like DHCPv6 to get that kind of remote device-level tracking.