its never going to happen its part of the goldbug dogma, currencies crash against other currencies, when they crash against commodities its called inflation.
If the worlds currencies crashed against gold then governments would regulate gold to stop it, they have done this throughout history, golds be money for 5000 years and throughout that time governments have controlled the price of gold, folks who think they will be buying their slab of VB with gold dreaming
yes we could return to the gold standard or commodity standard currencies although in every era that that has ever occurred before the price of gold was set by the government of the day