When all the big services become IPv6, the number of IPv4 megabits will become small.

You might just direct all the v4 traffic via a tunnel to another ISP which specializes in legacy services like IPv4, running SMTP/news servers, etc. Now you've saved all the cost of maintaining all the IPv4 peerings and config.

>When all the big services become IPv6, the number of IPv4 megabits will become small.

Well I have been hearing about the end of IPv4, and IP exhaustion for about 20 years now, and I fully expect people to still being moaning about it 20+ years from now while the majority of the interment still communicates over ipv4

Amen. I dual stacked my home network 10 years ago. 5 years ago I joined an ISP that gave me CGNATv4 and IPv6 and I opted to disable IPv6 at the router.

Why? If you have an IPv4 address, even a dynamic one, then IPv6 may not offer you a lot of practical benefit, but CGNAT-only sucks if you're at all technical.

It sucks if you're non-technical too, it's just harder for non-technical users to figure out the underlying source of any problems they have.

v6 also has better measured performance on webpage load times. Perhaps "pages load slightly slower than they could do" isn't a show-stopping problem, but faster would still be better, right?

CGNAT specifically means you can't have even temporary peer-to-peer connections, e.g. non-server multiplayer games generally won't work. And forget about trying to host anything, dynamic DNS services can't help you here. That to me is a much bigger problem than IPv4 in general being a bit slower.