China, Russia, and India have cut deals in which they agree to accept each others' currencies for bi-lateral trade while Europe, obviously, designed the euro to be a reserve asset and international medium of exchange.

These were challenges to the dollar's dominance, but they weren't mortal threats.

What's happening lately, however, is a lot more serious.

http://www.zerohedge.com/news/2017-09-16/suddenly-de-dollarization-thing