Personally, I will never see this happen. Crypto will exist but fiat will exist as well. They will co-exist because they have different features.
We both need fiat and crypto. In my opinion, we can reap the benefits of both crypto and fiat so why any of the two should disappear?
it's true that you conveyed it to replace the function of fiat currency I think it is very difficult because we know for now that bitcoin or crypto currency is still underestimated, the possibility that will happen is good cooperation between the two types of currencies that are different in nature and type