The car in question appears to be an E63 S Wagon with a camouflage wrap covering everything below the waist. Look closely and you'll see that the fenders have been significantly widened. The wagon is also wearing what appears to be the same wheel and tire setup from the AMG GT sedan that we saw yesterday. There's been no indication from Mercedes that there is a hotter version of the wagon in the works, but we're not complaining.
The driver of the E63 doesn't appear to be holding anything back, even getting up on three wheels in some spots. There are lots of theories about what this may be. Some are saying it's the return of the Black Series moniker or maybe an E63 R, similar to the Mercedes-AMG GT S and GT R. If that's the case, look for close to 650 horsepower from some variant of the twin-turbocharged 4.0-liter V8 from other AMG products.