China has better trade relationships with more of the rest of the world than the US does, (especially thanks to recent policy changes by the US Gov't).

The only requirement to be the worlds reserve currency is that everyone has to keep it in reserve in order to trade later. One can imagine that if China has trade relationships with the rest of the world, they would begin to stockpile more of the Yuan to keep in reserve, and as a result, the need for the dollar would become lesser.

Other than that, pricing commodities would be the next thing that would need to change, and that's not that hard. I could see a world where we move to 3 different reserve currencies based on the biggest economic powers and then, if the current administration continues its stupid trade war, everyone stops needing to hold onto as many dollars.