I really do not see a future where Crypto replaces Fiat. Honestly, such a future is not desirable. Even if it was desirable, quite a number of factors will not permit it to happen. I think the first major factor is government. Governments will never allow the eradication of Fiat currency. The eradication of Fiat will also mean the eradication of central banks. And this will mean complete loss of economic control by the government. I don't see any government letting this happen. Unless of course digital currencies will cease to be the way they are presently and face some really stiff regulation.