In my opinion, US dallar can't be replace by any currency, it is the king of fiats currencies just like bitcoin remains the king all coins/tokens. The Chinese yuan can not, and will not dominate the US dallar no matter how the Chinese economy is booming, the western nations will always be ahead of other countries in many ways including the world economic affairs. China will always make some impact but will not dominate USA/Britain, these two nations are the pointer to whether on economy, political, technology, matters etc.