For now cryptocurrency really trend all over the world, but still Fiat is much more prevailing than crypto. Which means, Fiat will exist as long as the government declare it as a useful thing to all citizens in the entire world. Even, though some are saying that Bitcoin could possibly has a potentials to become a world currency, but still just speculation at the moment.
I look for the future in a few decades bitcoin might be equated with fiat money, the difference is that fiat money is physical while bitcoin has no physical. The function is the same, namely as a payment instrument. People are given a choice, can use bitcoin or with fiat money for payment. If that happens, I prefer to use bitcoin.