you are describing an impossible scenario where nobody notices but overnight it becomes a global standard. if you actually make a scenario that is possible you

you are describing an impossible scenario where nobody notices but overnight it becomes a global standard. if you actually make a scenario that is possible you will see most people would have time to switch to the other and the original will slowly fade. no problem with that. dollar will sometime fade too for something else as all other currencies have done in the past (google some charts online)