In my opinion. until any time the fiat currency will be needed and used throughout the world. technological advances in the financial sector will not affect the existence of fiat currencies. Digital currency is used to facilitate everyone in choosing transaction tools so that our work will be easier. and fiat currency is used for people who do not have a digital currency.
Digital currency has no relevance with the fiat currency for it has different functions and roles that will be intended to. Decentralized digital currency maybe useful especiallly in terms of payment where it offers P2p transactions that could minimize transaction fees. However it still need digital equipment and internet so there are disadvantages of using it also. For now digital crypto currency is not yet user friendly and this.might systrm might put to ignore.