Are the Saudis running out of oil? Some people seem to think so, and this certainly bolsters their case.
We may see the oil economy drop off substantially in the next couple decades. $20 gas by 2020? Wouldn't surprise me. In fact, I'd be quite surprised if it's still under $5 by then. It won't help the economy; we might even see a global GDP contraction of 10% or more as we undergo a painful transition to other (more expensive) energy sources, until new technology brings power prices down again. I certainly expect to see a LOT more hybrid vehicles out there by 2010.
We won't totally run out of oil in my lifetime because oil fields run down gradually, and at higher prices oil can be extracted economically from places that aren't viable at lower prices, but I think we're going to badly miss cheap oil, at least until fusion power production technologies become commercially workable, and that won't happen until at least 2050 and probably not before 2070.
In the meantime we'd better get those pebble-bed nuke plants up, and look at bumping ethanol up to 20% of domestic gas consumption. This might be one good way to do it.