The important milestone is when it's safe to turn IPv4 off. And that's not going to happen as long as any country hasn't fully adopted it, and I don't think that's ever going to happen. For better or worse NAT handles outgoing connections and SNI routing handles incoming connections for most use cases. Self-hosting is the most broken but IMO that's better handled with tunneling anyway so you don't expose your home IP.
DS-lite (aka CGNAT), now we don't need to give the costumers a proper IP address anymore. It should be banned as it limits IPv6 adoption and it getting more and more use for "customers own good" and is annoying as hell to work around.
