Looks too much like a Ferrari to me.
My tip is: Make the back totally round, not with a "lip" where the exhausts are.
Dump the hollow doors and dump the air intake.
I think this will be a front engine car, so only need for smaller vents for the rear brakes.
My bet is the Panamera will look very much like the Cayenne, since the Cayenne is their biggest seller. Would also make sense to convert the design to a sedan.
BMW and Audi went the other way: Built an SUV (Superfluous Useless Vehicle) from a sedan...so I think Porsche will simply reverse that process.