Buddy, if you are talking about the track wouldn't it make sense to compare the Cayman to BMW's track car (the CSL)?
Porsche BETTER have 8 cars that lap the ring under 8 min. Probably more if you start taking every variant into account, C4S, C4S Targa, C4S Cab, if you really want to play that game.
It does not surprise me BMW does not have X6's, 650i's, X5's, Z4's, 328's, 128's, etc. lapping under 8 minutes as they have a much more diverse production lineup. I can't wait to see how the Panamera stacks up to the M5. We basically know it is going to be using the Cayenne powertrain and transmisisons, if so, it is all about profit not about racing heritage or heart.
M cars are special, they don't throw any motor or suspension in them. You won't see an M3 motor in everything else, M is not AMG.
I would hope the GT3 embarrasses the CSL, more power, less weight, and only a couple seconds on the Ring. What is more impressive, how close the BMW is with an older chassis and motor for less money, or how far ahead the GT3 is?