The test car is also wearing a larger rear spoiler than the current production M4 and has gained new LED tail-lights, as well as LED headlight details to match the facelifted 3 Series, as has been seen on the standard 4 Series Gran Coupé during testing.
These changes match up with the 4 Series Gran Coupé test mule we spotted earlier this year, with the facelifted M4 due for release a few months after this.
No major mechanical upgrades are expected for the 2017 M4, so power will still come from the same twin-turbocharged straight-six engine as today’s production model, but output will be increased beyond the 425bhp and 406lb ft of torque produced by the current car.
The M4’s engine is proven to be able to produce substantially more power. The GTS, with its efficiency improving water injection system, outputs 493bhp. However, the regular 2017 M4 will likely offer a figure closer to that of the current 444bhp M4 Competition Pack.
Inside, little is expected to change from today’s M4. BMW’s range-topping 7 Series has demonstrated the level of autonomous technology the manufacturer has available, but the 4 Series and M4 are unlikely to inherit such systems until the next all-new model is launched later this decade.
Due to the limited production numbers of the M4 GTS, it doesn’t look like BMW will be producing a facelifted version of that car. The most powerful M4 on offer next year will therefore be the M4 Competition Pack, which could produce something in the region of 460bhp.
Like the current model, when the facelifted M4 lands next year it’ll go up against the Mercedes-AMG C 63 and all-electric Tesla Model S. The M4’s coupé bodyshape also means the Porsche 911 is a more focused rival. An all-new 911 is due in 2018.