With the proliferation of SUVs, BMW’s M division has been redirecting some of its R&D resources to models such as the X5 M and X6 M along with their smaller counterparts, the X3 M and X4 M. At the same time, they have been working on several M Performance models, as small as the X2 M35i and as large as the X7 M50i. With an X8 M rumoured on the way, some would be tempted to say BMW’s go-faster division has been putting saloons on the back burner.

That’s actually not the case when you take into account BMW has actually extended its performance saloon lineup with the M235i Gran Coupe serving as an AMG CLA 35 and Audi S3 Saloon fighter. Not only that, but the hottest M-branded saloon of them all is coming quite possibly later this year as the M5 CS. A step above the already extremely potent M5 Competition, the new flavour of the four-door supercar has been spotted racking up test miles at the Nürburgring.

Gallery: BMW M Performance Parts for M5 Competition (2020)

From the new front spoiler lip to the CS-specific boot lid spoiler, you can easily tell we’re dealing with the M5 CS. The prototype seemed as if it was glued to the road thanks to the stiffer suspension setup bringing a visibly lower ride height. Some would argue the soundtrack delivered by the engine isn’t as exciting as it should be, but there could be an explanation. Euro-spec cars will get the petrol particulate filter expected to have a negative impact on the noise delivered by the twin-turbo 4.4-litre unit.

Speaking of which, the V8 already makes an astounding 617 bhp in the M5 Competition, so it will be interesting to see how much extra power the engineers are going to unlock. We’ve heard through the grapevine the output could grow to nearly 650 bhp, but nothing is official at this point. Whatever the power bump will be, it’s rumoured the CS will also come with a minor weight loss. A diet is exactly what the doctor ordered considering M5s have gotten larger and heavier with each new generation.

The wraps should come off late this year and there’s a pretty good chance the M5 CS will end up as a limited-run special edition. Price? Certainly above the M5 Competition available in the United Kingdom from £100,850.