Don't forget FDR's banning private ownership of gold and then changing the value of the dollar from around $20 and ounce to $35 and ounce.
It'll be interesting to see what happens now. I suspect the Russians will play silly buggers because they seem to enjoy that. And they have significant oil to play silly buggers with.
I have no doubts they'll all increase trade together, including military hardware, but establishing a reserve currency requires trust and dependency.
Those seem heavy loads for the ties of pragmatism and convenience that bind BRICS together.