The other useful function of these intentional spy shot releases is the same as that of prototypes at car shows: to prepare the buying public to a new look. We all had this reaction where, upon a new model's release, we recoil and immediately think "They ruined it!" Only to start liking it after it grows on us, a few months (or a year) later. So this is part of "socializing" the new look or the very different design language, prior to launch, so the initial uptake will be solid (the worst thing is for data to start coming in showing that a new model is not selling well; see, e.g., the new Honda Accord in the US.) 

Is it any surprise that these leaks of the yellow 911 are rear shots? It is the rear that is radically different from the current models...