Fair. I bet that'll change soon though. My prediction is that it'll be a mobile-first game, like the next Pokemon Go sort of thing, that'll be IPv6-only.

I agree it would probably be something mobile-first that does it, since those carriers all(?) support v6.

Plenty of mobile users use wifi at home/work. Telling them to disable their ipv4-only wifi just to play your game is going to be a non-starter, especially when the cost of ipv4 address adds negligible cost to infrastructure. Is your CTO really going to massively increase user friction ("turn of your wifi to play!") just so try to save a few cents (comparatively speaking) on infra?

It could be in a country where people don't have home wifi.

Like africa which does not have a shortage of V4 address and there is effectively no v6 rollout?

this isn't true. I know because at some point XFinity started dropping ipv6 connections for me and I noticed because a number of sites (forget which) were broken

What do you mean by dropping ipv6 connections, like dropping ipv6 packets? That's only an issue if you're using v6. I disabled ipv6 on my router years ago and have never had a problem just using v4.

I ran an ipv6-only website because that's the only way I can have a publicly routeable address at home. Just as an anecdote.