Not necessarily as the big country like China are creating their own currency, it's safe that way that they are the ones creating their own, but then its still centralized, it's not what people wanted, they can still print money like printing fiat.
the management system might be more different from the savings on fiat money printing costs which might be reduced when each country could make their crypto. however, we will see how later fiat will be abandoned with technology to use new currencies in the future.
Fiat can't be abandoned, both crypto and Fiat will always co exist in the future, people or users are the ones to determine here and I bet not all are tech savvy, even if all the whole world knows how to use crypto we will still want to use Fiat