Mystery plug behind rear seat in '07 DC

I was just searching around in the rear seat area of my DC. I found this unused plug behind the drivers side rear seat. It was on the lower back cab wall behind some vinyl sheet covering it.
Any ideas what it would have connected to? There's only one and there's none on the passenger side. Maybe it's for an optional woofer?

 

My Limited has a Sub_Woofer back there, so that would be my guess also.

 

subwoofer most likely

 

Either a sub or electric slider rear window.
Not sure if 2007 offered the electric slider though..

 

Yes the slider was available. I could now try searching the wiring diagrams since we've narrowed down a few possibilities.