I think it is very unlikely that replacing crypto with fiat is a good thing because people are confident in using fiat and to change that completely is not easy. Crypto and fiat can all co-exist to help balance the financial markets. Replacing fiat is not required at this time.
even now it is very difficult to see that happening. so many types of crypto at the moment, and the most certain thing is the price is very unstable. the price changes sometimes so far in a short time. moreover not everyone accepts it. well, because crypto still doesn't meet the requirements to replace money.