Can we get rid of banknotes and coins?
Money will always be used for exchanges between nations. As a universal equivalent it will still be the best commodity for nation-to-nation exchanges and for measuring debts and credits between nations too. 
Besides using alternative open source equivalents, such as cryptocurrencies, how would national banks manage to regulate inflation rates? This certainly is a critical point. Bitcoin for instance is a finite source of exchange: if it were to become a universal equivalent, virtually it would infinitely increase in its value, since the volume of the market exchange gets bigger and bigger.  Other cryptocurrencies tried solving this creating non finite sources, yet this still implies a arbitrary growth of the volume of available currency.