Question about head unit swap

Question for all the experts here. I am swapping out stock head units in my 2012 and have a question as to what the plug circled below is for.

I currently have a stock head unit (non JBL) and am simply putting in a touch screen (non navi, non JBL) from a 2013. Everything seems to be plug and play, with a couple adapters, but the grey plug remains empty. Any body know? Maybe use?

 

Without knowing for sure, but looking at the picture, the grey plug on the new one looks like a slightly different version of the blue plug. (blue only has one guide on top and grey has two guides on the top portion)

 

I believe blue plug on the old head unit was for XM radio. New unit doesn't seem to have this but not worried as I never even used it.

 

On mine '13 jbl, xm is built into the radio. Navigation would be the external module that bolts underneath. The white plug next to the grey one is where the navigation plugs into. On the navigation module is where the usb/aux plugs into and then jumps to the grey plug on the radio.