If that is the case both Mercedes and Audi will have 4.0 liter V8's in their sport coupes while BMW will offer the smallest displacement at 3.0 liters and two less cylinders. As the latest comparison test featuring the RS5 versus the C63 showed the RS5 4.2 liter naturally aspirated V8 is simply outmatched in grunt by Mercedes and BMW.
What will output be? Considering this motor should be a variant a 4.0 TFSI seen in the S6, S7, S8, RS6, RS7, etc., power ranging from 420 horsepower 560 horsepower Audi can pick and choose which flavor of the 4.0 TFSI they want to use based on what Mercedes does with the M177 4.0 liter twin turbo in the C63.
The advantage the RS5 will offer is all wheel drive (no 4Matic all wheel drive for the C63) as well as dual clutch and manual options. The C63 will again offer an automatic so the only dual clutch rival in the segment is BMW.
If this information is all correct, the RS5 may be the winner of the next generation battle.