When considering BRICS’s future, it’s important to remember that India and China are systemic rivals. Competition between them will likely intensify, given nationalism, border disputes and competition in the South China Sea. And although countries’ motivations for wanting to join BRICS differ, few global south nations will exchange one hegemon (the US) with another (China). And then, China is brutally on 12 Chinese Muslims which is contradictory to Saudi Arabia being the birthplace of Muhammad and Islam.
There is no prospect of a replacement for the dollar in the foreseeable future. Trade among BRICS countries is too small to sustain a common currency. It only makes sense to trade in national currencies (not freely convertible) if the trade balance between the countries is more or less equal.
And then Russia with all its border disputes is another problem.
China, by itself has the largest number of neighbors (14) sharing its 22,000 km land borders namely: North Korea, Russia, Mongolia, Kazakhstan, Kyrgyzstan, Tajikistan, Afghanistan, Pakistan, India, Nepal, Bhutan, Myanmar, Laos and Vietnam and China is embroiled in territorial disputes all of them.