I don't think cryptocurrencies will disappear. Cryptocurrencies allow you to make very cheap and fast payments between users. This is a real benefit that is in demand. Bitcoin and major cryptocurrencies will not disappear
For me cryptocurrency will not be disappear because as of now many cryptos are really trusted by many people and there are so many good benefits we are getting on cryptocurrency, that's why i am confident that crypto will be more popular in the future.
And don't forget that for the transfer of money banks take high fees. If you use cryptocurrency, it will be much cheaper. No one likes to pay big fees and then wait a few days for their money