Anything is possible, a massive war could break out and oil, copper, nickel and steel could be the most valuable. And the ones stockpiling steel and copper would win. Or precious metals could take off due to new technologies needing them. Thats why its important to diversify into various commodities.

Like ewasted said new products being more expensive. And that is definitely happening, look at what palladium and platinum have done in recent years due to emissions demand. What will happen once the car boom in china is over to the prices of platinum and palladium?

a worldwide depression would cut industrial demand to nothing, along with hyperinflation which would cause people to pull out of currencies and move into commodities