Maybe in the future but I think it will take time because some governments are not yet familiar with digital currency and some countries are not that much favorable with digital currency... It think with more explanation and discussion about the advantage of digital currency over fiat people will soon be more intrested to it...
It is written in the future book surely that digital currency will replace the cash, the reason for this is there is a lot of scope of growing profit in digital one as compared to money in pockets and in coming 5 to 6 years everyone will deal in digital currency so be ready for that time and there is also a ease in using digital currency. It gives a lot as compared to flat.