Very soon, I think. The cash just dissapiar from our life in next 15-25 years. The humanity just change cash and will use only other pay systems.
In some countries this change will happen sooner, some countries announced that in next 5 years to happen .we are definitely going in that direction, cashless society is now a global goal. Cryptocurrencies will speed up that proces, technology is main occupation of all the people, cryptocurrencies will dominate on global market in few years, and when younger generations grow up they will see cash only in museums.