I dont think gas prices will have any effect on the resell of a Wrangler. Owning a Wrangler is not like buying a car, it is more along the line of entering a Cult. Lets look at this in a real world light, just what does a Wrangler offer that makes it so popular. A short wheel base that delivers a rough ride. No real creature comfort in the form of either standard trim or options. Difficult entry and egress to the cab. Loud interior noise. Aerodynamics of a cinder block. Limited passenger space. Built by a company that could cease to exist at any time.
But on the flip side, it will run the Rubicon in stock form, provide transportation where many other vehicles can not. Quirky enough to make you smile. Doesn't look like every other vehicle on the road. Has a strong Cult following inspite of the long list above.
The only place that the MPG will come into play is when a dealership uses that excuse to lowball you on your trade in price. The end purchaser doesn't care about MPG.