CGNAT is also not cheap and very complex from a architectural point of view.
Vendors have been pushing it though, because implementing IPV6 only somehow is still a very, very scary thing for large ISP's to pull off.
what should happen is it should be very easy to deploy ipv6/4 translation mechanisms in ipv4 only networks, this would allow easy interopability and make it easier for the large networks to push IPV6.
CGNAT is also not cheap and very complex from a architectural point of view.
Vendors have been pushing it though, because implementing IPV6 only somehow is still a very, very scary thing for large ISP's to pull off.
what should happen is it should be very easy to deploy ipv6/4 translation mechanisms in ipv4 only networks, this would allow easy interopability and make it easier for the large networks to push IPV6.