CNY displacing USD would entail allowing people outside China to buy really significant quantities of CNY-denominated financial products. This would entail CNY/USD changing so CNY is more expensive, because the default currency for financial products currently existing is USD. Which would slap a corresponding huge price increase with 0 increase in quality to all Chinese export. Which would murder Chinese manufacturing export. Which would entail laying off some grand proportion of an industry that employs 5% of the _human_ race. Which is why they're not gonna do that.