i think someday crypto really can change fiat fully, like rightnow in pandemic the virtual payment on e-wallet really help people to do some trancaction
Now there is a non-cash payment method for goods and services, so nothing new in this can bring to the economy cryptocurrency. Governments of various countries are now on the way to creating a national digital currency, which will replace Fiat.
No, they will not replace fiat. Just because some governments are creating their cryptocurrencies that doesn't mean they have the intention to replace national currencies. Besides cryptocurrency are not in the stage they could support economies and financial systems.
No regulation, no stability, fluctuations, volatility I suppose these are no characteristics that you would want from the currency you depend on.
So, cryptocurrencies and fiat money will function together and with time cryptocurrencies will develope and progress more but they will not replace fiat.