Currently, it is very impossible to get rid of fiat in this era. Maybe if fiat ever goes away, they should first establish the internet around the world before it happens to remove fiat around the world.
Because until the internet is established worldwide, fiat will never disappear and cryptocurrency will still be secondary as virtual money in the whole world in my own opinion only.
In order for fiat to disappear, that is, the currency of states, it is necessary for the states themselves to disappear. However, mankind does not yet know another form of social organization, except for the union in the state. Therefore, as long as states exist, their currency will exist, which they will protect.
Cryptocurrency, if it does not want to be destroyed by states, or at least driven into deep underground, it is necessary to peacefully coexist with the currencies of states and take its place in the existing global financial structure.