Apple has been demanding apps support IPv6 only for years now. They reject your app if it fails under NAT64. The end user side is mostly a solved problem.
For iOS maybe. Most of those applications are also using Apple's networking libraries and are effectively required to be on Apple's infinite software update treadmill to continue to be listed, keeping them young and hip in perpetuity. This is the upside to that treadmill, things are up to date or just stop working.
But I don't think that's representative. "Or just stop working" isn't a valid alternative to the rest of the world. Outside of mobile ecosystems and maybe web development most things aren't on these 6 to 12 month update cycles. It would be absolutely unreasonable to tell a hospital that every piece of hardware and software and MRI machine in their building has to be upgraded every 2 years or it's positively geriatric and do you even `pacman -Syyu` bro?
Theres a whole world of things that haven't been, and may never be, transitioned. Useful things like utility control computers and even peoples' 10 year old, still perfectly functional and supported desktops. Heck, my "end user" newly-installed fibre ISP doesn't support IPv6! And their previous DSL installation to the same address did! So much for "solved problem" :(
A hospital's MRI machine doesn't need an internet connection. IPv4 only intranets are fine and we are never going to get rid of them.
But anything that connects to the internet needs to be updated regularly, if only for security and vulnerability reasons. If you have a 10-year-old functional and supported desktop, it most likely supports being IPv6 only just fine. The typical 10-year-old desktop came from the factory with Windows 8 and could be upgraded to Windows 10 (since it's supported). It even gets relatively new features such as IPv6 RDNSS allowing DHCP-less deployments.
