Detroit's big auto makers are slashing jobs, closing factories and undertaking costly revamps of their product strategies to cope with $4 a gallon gas. What's the worst thing that could happen now? Gas could get cheap again, says the man who runs America's biggest auto retailer.

"For once we actually have viable alternatives and exciting technology that are really game changers" in the effort to wean transportation from petroleum, says Mike Jackson, chairman and chief executive officer of AutoNation Inc. "However, if the price...