I honestly don't think it'll happen, certainly not in 15 years... In 100 years maybe?
Yeah I also agree with it, bitcoin can't replace dollar for to short of time. But maybe in 100 years from now will see.
even for the long term bitcoin will not be able to replace the dollar. here the government plays an important role. you can see the government's influence on bitcoin itself. when bitcoin is prohibited to circulate in a country with the ease give effecting to the bitcoin price in the market, I think any government will not want to replace their local currency to be replaced with bitcoin. it might make more sense if bitcoins replace the dollar only in terms for the international currency