Comment on The Road Not Taken: A World Where IPv4 Evolved by Tim

You keep talking about how this hypothetical IPv4x has "no flag day", but then mention "those last few IPv4‑only sites simply failed", which suggests there is still a discontinuity. What is the practical difference between a flag day, and a day beyond which some domains simply stop working and users are told to accept that breakage? One day, your packets get routed there, and the next day, unless you've upgraded all the right systems, your packets aren't. That sounds very much like a flag day to me.

IPv6 is the rarest of beasts: a case where the better long-term solution is actually winning out over the quick-n-dirty solution.