I don't think so that cash is going anywhere else,  until the next fifty sixty years.  Cash is now being the most basic form used by everyone,  everyone may do not have a credit card or a bank account but they do have access to cash.  Cash us the most basic form of currency.  Any cryptocurrencies or any other advancement will not replace it that easily. Bitcoin is continously growing up and it's price are skyrocketting and still very less people know about it.  I think cash will not be replaced.