I believe that will be happened in future but for that, need long time to fulfill. although I'm not sure about bitcoin even others Crypto cause its hard for any crypto to take place as one world digital currency.crypto aren't still enough secure, not stable, even can be manipulate.so don't think can be substitution for fiat.maybe something new invension is waiting for us for make one world order
It's an illusion to even think that there will come a time when there'll be one universal cryptocurrency used worldwide, or to think crypto will ever rrplace FIAT. Let's assume there is going to be a currency used universally worldwide, it's never going to be any existing cryptocurrency. The world powers understand the risk involved in doing such, hence I doubt if it will ever be obtainable.