Stopped by the dealer today to order the harness and was told that the 2010 catalog shows a 4 way harness for 07-09 (Trailer Tow Wiring Harness 82210213), but a 7 way harness for 2010 (Tow Vehicle Wiring Harness 82211156AB). He said he couldn't guarantee that the 4 way harness would work. I didn't order it out of caution. The official Mopar accessories site lists both, but under different sections.
Looking at the diagram, it looks as though the 7 Way harness is used if I want to tow my Jeep behind another vehicle.
Please, someone give me some insight.