I'm sure there was a time a century in arears when the planet elders were concerned for the future generations' coal and iron supply - and before them the planet elders were concerned for future generations' supply of wood.
Given what we know about the rate of techological advance (past and present), there's a damn good chance petroleum based products will take their place among other former primary natural resource.
I'm betting on sand and seawater becoming precious commodities in the distant future - I of course wont be around to be proven either right or wrong. ;-)
WmB