@marlathetourist they will use this only for settlement for international trade(cross-border) payments. fiat is not going anywhere. this is merely to prevent overuse or manipulation by a single currency, like usd. this way, they peg their local currency to the settlement currency, make the trade and the other side gets their money converted back from the settlement currency to their local currency. so the intermediary currency serves as trade stabiliser.
@marlathetourist it's essentially gold backed digital currency that can be used solely for international trade. you can also redeem it and get the gold(i think). Andy Schectman talks a lot about this.