Bitcoin is the Future: Countries that have flawed currencies are turning towards Bitcoin/ Crypto: FACT
FIAT will fail because it went off the gold standard!
FIAT will implode eventually!
The founder of Bitcoin understood this: He was and is a genius!
well its too bold to say fiat is useless and going to fail. I just believe why bitcoin or altcoins is future cause they seems good and could turn out to be a currency for transaction but i believe it would be true cause human live is keep developing and this technology is really good to be use for transaction. Despite all of good reasons there is a real problem with cryptocurrency, crypto are to volatile and too complicated for some people. So i believe many people would stick into fiat currency.
I do not even believe fiats will fail. They have not failed over the years and governments have a way of still pushing it out there. However, with respect to your statement of crypto being volatile, this is still a new space and of course the currency aspect of it is not being utilized fully which is what makes it a whole lot speculative in nature and results to the increase in volatility.
For what it is worth, I believe this is something that would change over time, and for sure will become an alternative to fiat, but cannot be for everybody just as you said in some people feeling it is a whole lot complicated for them and would rather stick to fiat.