I would not miss cash, I am more likely a digital orientated person. But yes, cryptocurrencies would take out control of the hand of governments, which surely they would not support.
I think that fiat will continue for long time while paper currency will be replaced by cryptocurrency because crypto is not centralized and fiat is owned by government and small entrepreneurs will use fiat for their transaction. But most of the people will use digital currency in the future, because it has more features and easy to use than fiat currency