The M157 in comparison even in the new AMG S models when rated at 585 horsepower is at 106 horsepower per liter. This motor is hardly stressed as aftermarket tunes gaining over 100 horsepower (at the wheels) show. Not to mention there are turbo upgrades out and a plethora of motors that can be shown as an example of more horsepower with far less displacement. The Supra, the Nissan GT-R, BMW E46 M3, all of these have shown triple digit figures from comparatively small six-cylinders.
AMG themselves adds power to these motors with just a software flash so what Tobias is peddling here is a load of BS. What is going to happen is the new 4.0 liter M177/M178 motor under development will eventually replace the M157. Downsizing to meet emissions standards is simply a reality that is taking place with OEM manufacturers.
Plus it is not like the smaller motor will be less stressed than the M157 and hybrid technology is not the solution for making up the displacement disadvantage especially with the weight a hybrid drivetrain adds.
Regardless, it seems hybrids are the future for AMG, "It’s clear depending on the segment – large SUVs, S-Class, whatever – in the future they will be assisted by electric motors… but there is no decision done, it is a discussion that must be done.” This he states despite no official decision on it yet.
Gentlemen, enjoy the golden age of internal combustion horsepower while it lasts. The future will be filled with smaller motors assisted by electric motors.