IPv4 reminds me non-Unicode applications from 90s
Or ATM, or frame-relay or IPX, or SNA, or 16bit DOS apps.
All above were gone eventually. SAme going to happen with IPv4, but I guess at slower rate.
Frame Relay and ATM are still very much living, so are non-Unicode applications, SNA and 16-bit DOS applications a little less so, IPX I think is all but dead however.