Will the U.S. dollar soon lose its status as the world’s pre-eminent currency? The consensus is no—it’s said that any move away from the dollar would take decades. This view is too complacent.

Developments in foreign-exchange markets during the past 18 months point toward dedollarization. Consider that Chinese “petroyuan” crude-oil futures, launched last year in Shanghai, now sit right behind Brent and West Texas Intermediate in trade volume. The world’s central banks bought more gold last year than at any time since President...