Working, functional partnership do not dissolve easily. The Eu, despite all its problems is a good example. Even the US-controlled system was one - it had a lot of disadvantages, but it worked to some degree, and it kept going on.
BRICS and the analogues that are converging with it are multilateral, egalitarian partnerships that worked well for all their participants, totally independent of the US. Some favored US allies kept increasing their BRICS participation even while they got a lot of benefits from the US. So its unlikely that they would just leave.
To simplify, BRICS and its analogues seem to be what the WTO would be without the 'special rules based order' that the US was subjecting everyone to, and the blackmailing influence of the Anglosaxon dominated financial system. (as can be seen from what happened recently with 'sanctions' and the resulting confiscations of money).
That was the last straw actually, all the countries that are rushing to BRICS as of this moment, started those initiatives immediately after 'asset seizures', or, rather, theft, that was effected on their enemies by the US, the UK and the supposedly neutral Switzerland. The 'neutrality' was discovered to be a farce and the 'rules based order' discovered to be able to change its rules whenever, however it suit its rule-makers.
The result is everyone applying to BRICS membership or observer status...