-snip-
I mean before anyone could trade among these 195 you need any of those currency to be able to travel across, and if only 6 countries decides to breakout from USD how do you think it will affect the US dollar?
There will be no much effects
It still depends on a number of things. Just judge their economic strength and how much they do business with other countries. If other countries depend a lot for business on BRICS countries where some of them are known to be slowly becoming "super power" countries, then they are enough to bring influence in the de-dollarization movement.