I think not, fiat money will never be replaced by bitcoin.
This is a parable, you can see what the OP says.
Lets say crypto completely and utterly replaced fiat.
because it is the tool we use for the current exchange, bitcoin is more suitable for the investment tool.
Time alwasy change, you will never know what will happen in the future. Keep in mind, bitcoin is made for a payment system initially, but since many people use and make a volatile price is a reason why bitcoin to be use as a place of investment, this is the biggest missconception ever.
I will hold to your words that time always change. What horse owner said when he saw car for the first time? Nobody will use this, or something similar, after decades horses didn`t disappear but who use them, who see them? In past century we have seen many changes, in my opinion its time for economy to change too. Crypto will replace fiat one day, that already started happen little by little and we are growing, in 10 or 50 years change will be complete.