Emperor - I see where you coming from, but surely they could use a mule from the upcoming Cayenne II and no one would be the wiser? People would think that they were just testing the new Cayenne rather than the new Panamera Coupe (GT). 

Anyway, this is all speculation (but great fun). I really hope that it is a mid-engined GT1 or the new 998 (991). The Panamera Coupe makes a lot of sense from a business point of veiw, but as a sportscar (read Porsche) enthusiast I would prefer to see a new earth shaterring, totally dedicated sportscar.