it can be happen if government accept bitcoin in their country and i think global can accept it as well

because bitcoin has high value than a us dollars and much profitable.
It will take decades for the bitcoin to be a global currency. In 2019, there might be 10 million people using it.
I expect it can be happened in the near future and i believe everybody will have same expectations as me right now, even bitcoin has more valuable than the giant us dollar it is mean nothing.
As long as nobody use it , bitcoin are just a useles currency.