I think it's very unlikely that crypto will replace fiat currency, fiat is easier to use as a payment medium and also has a more stable value. I am more confident that crypto will be used as an asset.
if crypto gets official regulations, then they will educate people with various uses through e-transactions in stages, physical currencies will be replaced soon in the next 10-20 years. the level of comfort in digital money is stronger and more efficient and in the end there will be many people who are familiar with it.