Hey guys, I'll post what I did a while back. BTW, I think the car in the beginning of the video posted is a C4s because of the sideskirts.  

First I want to say I did this rendering long before the 991 came out, and before we knew the tail lights would be recessed. So it would be perfectly possible to put the reflector on. Now that the tail lights are recessed, I think its even safe to confirm there won't be any reflector on the C4 models. But as it was with the 997, we might see one on the facelift.