Well I would hardly say that protections against being obliterated in a global ransomware attack that comes out after the ransomware attack occurs helps the victims that much but yes it is possible if there is another massive cyber attack Microsoft could release a fix for 10 years after support has ended.
It is definitely possible to heavily lockdown a Windows computer to prevent 99% of attacks and if you don’t need WAN access especially that becomes significantly easier.
It is far more likely browsers will drop support for 10 in a few years and that will be what stops the average user from being able to continue to use their Windows 10 computer.
Btw I do have a spare PC, it only got Win10 because the GPU didn't support 7, and it's not getting 11 even though it supports it. Microsoft's job to keep that secure.