Each country has its own economy and its currency, confirmed by a gold reserve. Digital money cant become a single world currency, because they are decentralized, i.e. arent controlled by anyone. But a crypto currency can remain a means of paying for some services or goods, like chips in a casino or as coupons.
Youre right on this dude,as existing currencies from all over the world will never lose their position instead cryptocurrency will help them make all the needed by the people
As i believe that virtual money created just for back up or like a gambling chips that the value will rely on the real currency