Did you see the outrage when they suggested requiring an internet connection? With the PS4 as a viable competitor they don't have the leverage to pull stuff like that.
The galling thing about the Internet connection requirement was that it was extremely overbearing DRM that inconvenienced users in many cases and benefitted them in none. Requiring IPv6 doesn't have the same stink about it.
He said "They should have made IPv6 mandatory", as in, it cannot use IPv4. Obviously, "when connecting to the Internet is required" is implied, and having an always online console is irrelevant to his point.
"technical" roadblocks like many routers in production punt IPv6 processing to their control plane, crashing performance?
There's lots of magic happening behind the scenes that'll suddenly collapse with such an influx of new users. See also: AT&T when the iPhone came out and proved their data capacity to be insufficient.
It turns out they are actually big problems. You can't dream them away. What would have actually happened is Microsoft would have had a customer revolt on their hands and not sold any Xbox One consoles -- I think they have enough problems without manufacturing one for no good reason.
I'm sure all the ISPs would then have suddenly found out that all those "technical" roadblocks to IPv6 migration weren't such a big problem after all.