[SCOTT26]

It's registered as an AG car for BMW M. As a street test prototype.
Now what is interesting is that the larger side intake and the rear spoiler almost like a duck tail not the huge wing sitting on top were part of the Aerodynamic pieces I saw.

Most of them were very smooth for Aerodynamic purposes rather than being over sculpted. The front aero intakes were closed off with the vertical air curtain exposed but the space of the intake was designed to allow the airflow into the curtain so it was sculpted.

I am willing to bet they are planning the final outing for the M4.
Now M4 is already pretty radical what with GTS and CS bonnet,hood and trunk fabricated from CFRP so optimising and smoothing off aerodynamics as well as other areas show at least CS, GTS and hypothetically CSL offer further progression.