In future, there will not traditional currencies, will be only crypto
You are mistaken. There are too many places in the world where the Internet cannot be used ever. People living there will never have any chances to deal with the crypto.
That is the biggest limitation of cryptocurrencies, some are proposing the creation of physical cryptocurrencies in order to overcome that limitation but I am not really sure that is going to work, it is better to accept the limitations of cryptocurrencies and deal with them, this means that the poorest people will be unable to get access to cryptocurrencies but this is something we have known for some time and unless the living standards improve a lot in the next decade this is something we will have to accept.