CGNAT (or comparable tech like DSlite) will happen anyways even when majority of traffic is IPv6. The long tail of IPv4 is long; people will be wanting some form of IPv4 connectivity long after all the major things have switched to IPv6 and ISPs are not going to go back to handing out public IPv4 addresses. The timeline just doesn't work anymore to make a clean transition. Of course how much do you care if it is CGNAT if you are not using IPv4 is another matter.