Well if the cryptocurrency gets really popular in the future it might happen because in the future everything we buy will probably be online.
So i think that it is possible for cryptocurrency like bitcoin can be such a important coin in the future that it will replace paper money.
It is hard to replace money by cryptocurrency, I am not closing the door for the possibilities but still don't agree for now to make real money disappear. Why not just an alternative just like checks, we can also use cryptocurrencies as a way of investment by business or and individual and can be an additions to their income.