Yes agree, the future of the financial world is cryptocurrency, we are not too late to follow, I'm sure 20 years longer all transactions will use the cryptocurrency.
I think it is impossible for all transactions to use cryptocurrency, this is because until now cryptocurrency is not in physical form so the use of cash is still a lot.
For now, but with the advancement of technology and in the future where all people has the access to internet and smartphones and devices then cryptocurrencies will be the future of transactions. But right now this is unlikely to happen because some countries are not advanced enough and people are not rich enough to provide such requirements.
In my opinion I think fiat will run for another 30 years.