alt Hacker NewsI was at a talk where he brought up exactly this (I also once did a talk alongside him, but that's a different story). He said there would be two changes:
1. It would have 128-bit addresses. 2. It would have end-to-end encryption (or was it authentication, I forget).
IPv6 was supposed to fix both of these, with IPsec mandatory, but the latter demand sort of faded out into obscurity. We ended up basically solving encryption by pushing everything into TLS anyway, which I guess solved much of the same problems although at a very different layer.
Doing this brings you close to OSI, which famously failed by being overcomplicated. The current design was implementable by zillions of cheap humans running cheap hardware.
I always wonder if the internet is thesurvivor of the networking cambrian explosion, with a slight roll of the dice making another candidate the winner.