Fair question! If I had to guess: the USA + Europe + Canada + Australia + a few other countries will form one trading block, and BRICS + about 20 other countries will form a separate trading block. The different trading blocks will use different reserve currencies. The BRICS+ trading block would use a basket of currencies and our trading block would use the US dollar, or a basket of currencies with the dollar being the largest percentage in the basket.
I love to travel and visit other countries and meet people. My hope is that a tourist will continue to be able to easily visit any country, even when the world bifurcates into two trading blocks.