Dollar will continue to be the best currency in all over the world and that won't change that quickly, unless world says something about it than we will have dollar used everywhere. I have recently (this past summer) went to a vacation in ukraine and I was capable of using my dollars anywhere I want and exchange it when I needed, I did not see chinese yuan there, I did not see russian ruble neither (might be political) there was only 3 currencies you could change, dollar/euro/pound (or sterlin I don't know what they call it).

Considering this won't change for a long time in almost everywhere than we can say that these holy trinity of money will continue to rule over the world for years to come. Maybe in distant future like 50 years from now we may see a rival but no matter what happens we will continue with these for now.