The BRICS can add as many members as it wants, but ultimately, the US has the final say. So long as the USD remains the reserve currency of the world. One way or another, countries need the USD to survive. It's hard to make use of another currency that would challenge the USD. I'd bet the next country to join the bloc is Venezuela.

Right now the USD is showing signs of weakness, so "de-dollarization" efforts would only accelerate. Especially now that Trump is threatening to fire FED chair Jerome Powell and threatening other countries with additional tariffs. This will only make countries reject the USD even more. Confidence among investors will be lost, due to the US' economic uncertainty. Without money pouring into US treasuries and bonds, the country will be doomed. It will be forced to default on its debt. Perhaps, the BRICS will survive and live alongside the EU bloc for generations. We never know what the future holds, so anything's possible.