There are so many possibilities in here if the cryptocurrency will remove or replaced FIAT currency there are some people that doesn't want to use it because they don't know. There are some good deeds it can provide like the faster transactions to any people who use it. But before that happen for sure it will gonna be world discuss.
There will be a huge debate about this thing for sure, and I know this will not happen easily. I actually don't see cryptos to replace fiat, if that is the case cryptos will become more centralize so for me its not a good idea to replace fiat. Better to make a healthy competition with it and let people decide on what to use base on their liquidity.
The reality on the above topic thread posted is Crypto currency transaction is not yet fully accepted by a lot countries where we belong, Crypto as main currency used for transaction or Replacing Fiat is still up in the air. Look at the imposed Banned by countries whom critical about crypto transaction, not to mention the issues on Banned, Scammer, Hacking, all of this are just few indicators that Replacing FIAT by Crypto is far from reality yet it has increase the growing number of Crypto investors.