Wrong if we think cryptocurrency and physical currencies will not collide. If cryptocurrency market received more attention, and majority of people in the world are familiar with bitcoin, then the global economy will change. This will not happen in the near future, only a third world war which could make it faster.
That is very impossible that bitcoin will replace dollar because people doesn't want to change the currency system of a country.
I will believe if gold will be the next currency and if the government will implement again the ancient times of law.
But with bitcoin, I really don't think it will happen.