At some point, though, the price may go up enough that it might as well be completely exhausted.
"Hubbert's Peak" is a canard, and I'm frankly amazed to see so many otherwise intelligent people accept it as the gospel truth.
Because of taxes, Europeans pay about double for gasoline that Americans do, yet they continue to buy it. I suggest it is even easier for Americans to pay that much. If the price of gas were to be about five bucks a gallon, expect all kinds of new sources to be developed that aren't being touched today. And on the other side of the coin, expect a lot of innovation in energy conservation.
A higher price will unlock motor fuels from other sources. Petroleum fuels might become scarce but liquid fuel will continue to be made. Too many people have a stake in continuing to sell the stuff.
So it's just a matter of price. Oil at my price is what I want.
And alas, $0.25 oil was exhausted long ago.
The price will go up gradually and consumption will decrease and alternative energy sources will become more attractive. This will not be an on or off situation.