The problem is that you can't really move completely to IPv6. You actually will have to run both IPv4 and IPv6 networks indefinitely. Which isn't a lot of fun.

Now, yes. But eventually, we'll reach a tipping point where that isn't necessary. When? Your guess is as good as mine.

"You actually will have to run both IPv4 and IPv6 networks *indefinitely*."

Sure you can. You can do it today even, let alone in some unspecified number of years.

We have been trying to deploy IPv6 for 20 years now. This would be comparatively easier and buy us another 20 years to finish v6 deployment.

A ton of old equipment would need to be upgraded to use 240/4 for IPv4 unicast. We'd run into weird issues where it works for some people and not others. I'm not convinced. If this was done 25 years ago, maybe.

And 50% of the internet traffic is IPv6. The proposal here is to introduce a separate (arguably harder) change which would start at 0% support again. Beyond that, it'd just be a temporary fix.

Just 240/4 allowed specifically for private network use (like the 10/8 range)... that I could get behind though. This would still exclude 255.255.255.255/32 of course.