Division head Tobias Moers has promised "there's still room for more" output from the GT's V8 engine.
The executive said "we started the journey for Black Series" and 2020 would make an "interesting year" for the brand, according to quotes posted by CarAdvice.
The 2017 facelift brought a slight power increase to 469 horsepower and 465 pound-feet of torque from the GT's base 4.0-liter twin-turbocharged V8, while the GT R currently boasts 577 ponies and 520 pound-feet of torque.
As rivals and Mercedes-AMG's own E63 push into the 600-horsepower range, the GT is under pressure to retake the lead as the brand's flagship.
Aside from expected engine tweaks, Moers says the new Black Series must feature something "really surprising." Additional details will likely trickle to the surface ahead of the 2020 arrival.