Sorry to dig up an old thread, but I just replaced my BA amp with the Kicker today and saw the unused blue connector. I do have a backup cam and reverse sensors but still have the unused connector. So I was also curious what it's for.
The only thing I can think of so far is that they use a common wiring harness for the WK and XK and that maybe it's for the rear AC on the XK?
2010 Brilliant Black Crystal Pearl Coat Grand Cherokee S-Limited with various bits 'n pieces... broken in but not even finished!