I don't think it's cameras... I actually think it has to do with the new European standards.There are rumors and speculation that Porsche is doing away with side mirrors and replacing them with cameras. If you look closely at the triangle at the forward edge of the side window...where the current model mirror attaches...something is there that very well may be a camera. The door mounted mirrors on the prototypes could be dummies.
Another school of thought has it that this new mirror design is real, and that they were re-designed to allow for motorized rotation to fold inwards.