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 would like to say my point of view, it will not replace FIAT in all matters even a hundred years of promotion, this is because FIAT is a government assets backed by GOLD, it is the only currency that is backed by the government. Talking about crypto, yes it can be a payment option only for most transactions only, but it does not mean it will replace FIAT in all sense.