Yes, Fiat will not be totally removed by it will decrease in its operation little by little because blockchain technology will be very busy that time. So crypto /Bitcoin will reign as future money.
In my opinion, bitcoin will not replace fiat money, but in line with what is needed. Because fiat money is issued by the central banks of each country, while bitcoin does not print and nobody controls. Bitcoin is digital money and applies throughout the world, where the system is decentralized and peer to peer.