very unlikely, even if the fiat currency will be replaced, it looks like gold is more suitable as a payment currency, a currency that will never experience inflation.
The use case of crypto is also better compared to gold so I believe people will see which are more valuable between the two but this will take time.
I know that people will not use gold as the gold was already been replaced by the fiat currencies. Its the matter of whether people will quit fiat and use digital currency instead ?
Well, not until bitcoin price is stabilized. I mean you will not want a person buying a car for some bitcoins and in the evening the price of the amount is reduced by 5 percent or so. This is the disadvantage of volatile currency. I hope with regulations this problem will be solved and then bitcoin will be used as a major currency.