It will take a long time for these countries to dethrone the dollar simply on demographic levels alone they are headed for economic stagnation.
I see BRICS as a framework for these countries when economies become more regionalized after the eventual collapse the world will feel from these demographic bombs.
There are not enough kids in China, Russia, Brazil, ect. They are not wealthy enough nations to do what Japan is doing with investment economies either.
Yes, the all poor countries like the BRICS have the same problem. Either you impose tight restrictions on your currency and limit its trading (like China and India) or your see regular cycles of hyperinflation and devaluation like Russia and Brazil.
They are all small boats on the sea that is the US dollar. Either they stay in port or accept being hit by storms.