What would likely happen, and is still a potential outcome if we don't help enough people opt out into Bitcoin, is the fiat ponzi would continue unabated until it was unsustainable. At which point, the system would collapse and a global surveillance currency issued likely by the IMF (digital SDR) would probably be used as the reserve currency. Many nations would use that as their domestic currency, while others just ran it back with a new version of their old currency. With more surveillance and control of course. US dollar would be the last fiat to fail.

I don't know how long we have until this future is a reality. Maybe 5 years, maybe 50 but we should all be pushing to help grow bitcoin adoption and education so the world is ready for the last battle when it arrives. Whether that battle is conducted by this generation of Bitcoiners or the next remains to be seen.