fiat and USD is never die, bitcoin and fiat currency is a very different, we can see that fiat currency is have the physical form, and bitcoin and other cryptocurrency is not have it, so i think bitcoin and fiat is different things, so fiat will never changed with bitcoin.
It is nonsense to say good bye for the traditional money. Fiat will never change the cryptocurrency for many people, especially those that live in the developing countries and in the poorest areas.