Experts believe that it is not possible to replace fiat currency with crypto. Since the transaction time and cost of crypto currencies are still high in comparison with credit cards so it is difficult to adapt it easily.

This is exactly what some cryptocurrencies are trying to accomplish. IOTA's tangle is what promises a fee-less and instant transaction time.

RaiBlocks also aims to tackle this issue.

I am certain that it is possible to replace FIAT with crypto. We only need to chose a method of implication and some time.