Hi @whyaskwhy, 

Here is [the list of the major reserve currencies](https://data.imf.org/regular.aspx?key=41175) of the world. 

In my opinion, there are three events that could shift the positions. 

First - The reliance on crude oil for our energy needs. When the world finally transitions from crude oil to other sources of energy and the world's reliance on crude oil is minimal, the agreement the U.S has with Saudi Arabia to sell oil in the U.S Dollar, would have no beneficial effect for the U.S. One of the main reasons why the U.S Dollar is still the reserve currency is because the Saudis are selling their crude in U.S dollars. 

Second - If and when Bitcoin becomes the reserve currency of the world. It would have sounded preposterous to say so, say, five years ago. Today, it is not so, although it looks a bit outlandish. How it will turn out in the future is hard to predict. 

Third - If and when China becomes the world's superpower and major trading partner of the world. China's ambitions are obvious. They want to become a superpower. Historically China has not been a country that showed interest in imperialism or colonialism. That was because of Chinese believe in Taoism, Buddhism and Confucianism. But all that changed with the advent of Communism in China. Although, the Chines people, by and large, probably still are influenced by these philosophies to some extent, their leaders are not. This non-believe in their traditional believe systems, allows their leaders to skirt around imperialism although communism per se, in my understanding,  is not imperialistic. 

China's rush to create a digital yuan is aimed at to, eventually, replace the U.S Dollar as the primary reserve currency.  They can easily do so, if and when China becomes the world's superpower and the major trading partner in the world. China becoming the world's superpower and the demise of crude oil as the major source of energy might just coincide. That would, all else being the same, certainly be a disaster for the U.S.