Will cryptocurrency someday be able to become a legal currency or legal tender?
If you look at the growth so far, it is not impossible that in the future all countries will use crypto as a substitute for fiat, but not all cryptos but cryptos that have the highest market capitalization rate, or even every country has its own crypto and that is already happening in several countries. We just need to continue to make good contributions so we can show crypto isn't as bad as the bankers say.
Yes. Some countries are eventually making their own digital coin as an alternative to their own fiat. While some countries are starting to notice bitcoin and planning to adopt it legally because the leaders of such countries have high hopes on the potentials of bitcoin.
But not all crypto are being acknowledge by some big merchants. Ethereum and bitcoin are still leading the adoption but hopefully, after a couple of years, they will start to be recognize. Bitcoin cannot replace fiat for now but it has high chances that fiat and bitcoin can both co exist.