i think fiat currency is still strong for now. the best achievement at this time is bitcoin can be a companion to fiat currency. and to replace it still takes a long time. Moreover, btc users are still minimal for now
Bitcoin will be able to walk along with fiat, it's hard for Bitcoin to replace fiat money because society is still very less knowledge about Cryptocurrency. So it will take a long time so that the public can use the Bitcoin or other Crypto correctly.
there are still so many shortcomings in bitcoin, or other cryptocurrency. I think that ETH can be a candidate, but seeing that the price is fast enough to go down, I think it is gone. well, for now maybe still too fast to say goodbye to fiat, and usd.