We know this will be a hatch thanks to a few details at the back. We first noticed that there's one continuous shut line on either side running from the top of the rear glass down into the sheetmetal. The shut lines don't continue into the taillights, though, instead running around the top edges and slightly downward before shooting across the middle high up in the rear fascia. With how short the rear deck is, a conventional trunk opening would be far too small, meaning the glass has to open up with the trunk in a hatch. This may seem a little odd at first, but it actually strengthens the connection to the AMG GT coupe, since it too is technically a hatchback.
The removal of fake body panels also reveals a shape that is very similar to the concept shown at the 2017 Geneva Motor Show. It has the same slender taillights, fastback roof line, and Panamericana grille as the concept, as well as the current coupe. The rear fascia also leans forward and is curt without any extraneous spoilers. It does lack the over-the-top lower diffuser and center exhaust of the concept, though.
Powertrain and reveal dates are somewhat of a mystery still. The concept had an 805-horsepower hybrid powertrain, but since the most potent GT coupe, the GT R, only makes 577 horsepower, we doubt the production four-door will have the concept's grunt. The company gave no timeline for the production car, but we would guess a production version will be shown sometime in 2018.