Hi,
found this one...by the way: back-windows is just fake. Beneath the back-window of this prototype the same vertical standing window as on the current 6 series cabrio can be seen (not on the foto).
On the other side, there is this huge crack separating the trunk lid from the rest of the body on a side-location - that would lead us to a cabrio-coupe (softtop normally don't need such a crack at the side - compare current crack-location at the e64-softtop-cover)
So I'm not sure...how about a F12 regular softtop cabrio and a F13 hardtop cabrio-coupé version?
That also could explain the unusual release-schedule F12(cabrio) first, F13(coupé) second. Would make more sense if "cabrio = softtop" and "coupe = hardtop cabrio-coupe".
But this is pure speculation...just don't know anything!
Have fun with the pics, tho...