Personally, I see the future without fiat money, but a full cashless settlement. The Internet currency is the currency of the future, there will be a word behind it.
I don't think so, whatever happen Fiat currency would not disappear. Fiat currency is controlled by a government and the good thing about it is that if something happens to your money you still have the chance to recover it by recovering all you bank transaction. Unlike crypto, if you make some mistakes you can never retrieve it anymore. And most of the time elders are no longer interested to learn this kind of technology and they prefer to use Fiat currency. So I think this could never happen, being a cashless society.