The Q8 concept (pictured), revealed at the Detroit motor show in January, utilised a new petrol-electric hybrid drivetrain consisting of a 245kW/500Nm 3.0-litre petrol engine and an electric motor pushing out combined outputs of 330kW and 700Nm – with 0-100km/h taking 5.4 seconds.
Meanwhile, the rumoured 'RS Q8' concept is expected to use the brand's 4.0-litre twin-turbo V8, which does service in numerous models including the RS6, RS7 and S8, along with the Bentley Continental.
In the RS6/RS7 Performance tune, the blown V8 produces 445kW of power and 700Nm of torque, good to propel the super sports wagon and liftback from 0-100km/h in just 3.7 seconds.
Should these rumours prove to be true, the RS Q8 concept would rival current production models like the BMW X6 M and Mercedes-Benz GLE63 S Coupe, which are both powered by twin-turbo V8s and boast 0-100km/h times of just over 4.0 seconds.
In addition to the performance powertrain, expect the RS Q8 concept to feature more aggressive styling than the already-bold Q8 shown in Detroit, along with sportier alloy wheels (the Q8 concept already had massive 23-inch rims) and numerous performance-oriented interior appointments.
Further details of the German performance SUV are still to be revealed, so we'll need to wait until the Geneva event next month to see if Autocar's claims are correct.
Stay tuned to CarAdvice for our coverage of the 2017 Geneva motor show.