Cryptocurrency is the future of all payment method due to the decentralized nature which grants financial freedom and power to the people. However, for it to replace cash or the Fiat, it will take years of awareness creation. Up to date, some people do not have access to internet whereas others do not know how to access it.
I haven't thought of a world where everything is virtual, so it's not going to happen, let me give you an example it's unimaginable you are on a far away place where there is no electricity and you have to pay for water, so what you are going to use, of course, fiat it's easy and common sense.