[Arnt]

The only realistic reason to get rid of IPv4 is its unreliability, if significant.

15-20 years ago IPv6 routing was often tunneled over v4, and it was noticeably less reliable than v4. Nowadays v6 is a touch faster/more reliable than v4, not very much. If that difference widens much and most users have v6 anyway, then v4 might get the axe. Otherwise... I don't think so.

FWIW I already operate some v6-only services. Not for the general audience. An SSH bastion host, a backup service, that kind of thing, not web sites for the general audience. I'm not in the least surprised if some warez topsite is v6-only already.