This is a very important question, but without a straight forward answer, come to think of it, the USD has been the world currency since the US has been the world power, aside this the China nation has been working so hard to lead in the world power but it has continued to be a fruitless effort, The US nation will not seat and watch that happen because for the Chinese Yuan to be the world's currency that simply means the Chinese nation rules the world.
What I'm saying in reply to the question is this, it will be very impossible, if there should be any possibility in it, it will be hell difficult.