For me,i believe that cryptocurrency will have its own time to vanish but it might happen maybe hundred years from now.
only useless cyptos will dissapear and they wont take over a hundred years but usefull and original cryptos such as bitcoin will remain to stay .
As long as blockchain is still present,then cryptos will surely go along with it too.
blockchain is a technology a useful technlogy so there is no point that it will dissapear because people will constantly use it as its more advance than other outdated technologies that we have today . there are also cryptos that are not based on blockchain . so there is no need to worry .