Shortly thereafter (if not before), governments will make it illegal to go online with a device that doesn't do a remote attestation with Secure Boot, and they'll require that the OS has a system like Gatekeeper[0] which checks a centrally-managed blacklist every time you try to run an application.
Most of us will have illegal, unregistered phones then, running hacked firmware. Just look at Russia, China or all the illegal satellite dishes on Saudi rooftops.
It's an arms race all the way to the collapse of the system (or revolution). Rinse, repeat.
> Most of us will have illegal, unregistered phones then, running hacked firmware.
How easy is it to hack an iPhone to make it run unsigned code, which reports to a remote server that it is running the latest iOS version (with the correct cryptographic proofs)?
Maybe other phones are more hackable right now, but I'm sure Apple wouldn't mind lobbying for a law that requires phones to meet the same standard as them, and that makes ISPs / mobile networks refuse access to any device whose Secure Boot implementation has been circumvented by "independent researchers".
Five years from now, the only people inconvenienced by such a draconian law will be 1) those whose phones run on completely Free Software, and 2) those who illegally import devices that use unpublished zero-days in order to commit highly profitable crimes online. Both groups will probably end up paying thousands of dollars per device, but governments will not care about the desires of either of them.
[0] https://www.howtogeek.com/701176/does-apple-track-every-mac-...