We've done so much learning about good UX, backwards compatibility and smooth upgrade paths in the years since IPv6 was first thought of and specified that I suggest there is a group of people out there (or on here) who can sensibly come up with an "IPv4.1" draft that can represent a smooth upgrade path from where we are right now, towards an extensible internet addressing format/protocol. It would have at least the following properties:

- IPv4-formatted addresses would continue to work as today - address space can be extended by adding bits to the existing IPv4 format, and 0 bits do not need to be typed out etc (in mathematical notation there's also no need to write 0001.200 if we just mean 1.2)

(It feels like there should be a couple more fundamental properties to be stated here, but I can't think of any more right now.)