I think it is very unlikely that we will see a worldwide crypto currency issued by a central bank since that will require a government so powerful that it can impose his will above the will of the other countries and while the U.S is very powerful is not that powerful.
Never say never.
There was no single country which was very powerful in the Euro zone. Yet, we did see the Euro replace the lira, drachma and the deutsche mark.
I tend to disgree. Germany (and France, to a degree) is a backbone of the European Union and its primary driver. And the Deutsche mark quite naturally was the strongest currency among the countries that united into the EU later. If you are going to challenge that point, you should keep in mind that the SDR currency maintained by the IMF included the US dollar, Deutsche mark, French franc, British pound and Japanese yen before the Euro replaced franc and mark. And the Deutsche mark had also been included in the basket of currencies used to calculate the US Dollar Index, a measure of the dollar strength...
So it seems that your claim is not founded on facts