This article is wrong.

  As oil becomes scarce, consumers will necessarily turn to
  an alternative before the supply runs out.

When something has become so scarce that it is necessary for everybody to turn to an alternative, you've run out of it. Yes, the world will always have oil, but it will gradually become so expensive that you can't buy it for any reasonable amount of money. We'll run out of oil in the same way that we've run out of bottles of wine from the 1600's: some will exist, but nobody can do anything with it because it's so rare and hard to get.