Downsizing engines doesn't necessarily mean less horsepower.
Many were quite concerned when BMW announced that their latest generation M5 (F10) was going to be powered by a 4.4-liter twin-turbo V8 instead of the outgoing model's (E60) naturally-aspirated 5.0-liter V10. Despite the fact that that wonderful V10 wouldn't return, BMW promised that the new M5 would be even more powerful and faster than its predecessor. Sure enough, they were correct. The F10 has 578hp compared to the E60's 500hp.
In this recently posted video, some Swedish M5 fans decided to take examples of each one out on a track just to see which one is faster.
With the next M3 set to be launched sometime next year, there's no question in our minds that it will be faster than the current generation, even though the latter is powered by a V8 and the new generation will likely have a twin-turbocharged inline six. Change is not always a bad thing.