It looks like Jeep's heard enough "minivan engine" jokes, and plans on beefing things up a bit. They'll use the same engine that the 2011 Grand Cherokee had in the new Wranglers.
From an article on carscoop.
In the announcement on Chrysler's third-quarter sales results, the company's CEO Sergio Marchionne confirmed that next year's 2012 Jeep Wrangler and Wrangler Unlimited will both get a new 3.6-liter V6 "Pentastar" engine. Mr. Marchionne also spoke of a new Dodge sedan as well, which is currently being developed on the underpinnings of the Alfa Romeo Giulietta hatchback.
The Pentastar V6 first debuted on the 2011 Jeep Grand Cherokee, and is gradually making its way on other models, including the 2011 Dodge Charger and Grand Caravan.
Now it's the Wrangler's turn, which received a significantly upgraded interior for the 2011 model year, but Jeep's modernizing efforts were somewhat overshadowed by the old 3.8-liter V6, capable of delivering 202 hp (151 kW).
The new engine will solve this problem, though output is not known yet. For the record, the the Pentastar V6 produces 283 hp (211 kW) and 305 hp (227 kW) on the aforementioned Dodge models.
From an article on carscoop.