February 28, 2017: A document containing the model codes for various future BMWs got into the hands of members of Bimmerpost. The document contained codes for models not yet announced as well as regions and drivetrains. Included on the list is the next-generation M5, and it specifically mentions that the M5 will have all-wheel-drive.
April 26, 2016: More photos come out of the BMW M5. More camouflage has come off, and this example sports current-model wheels and brakes. There's also the possibility the taillights pack OLED technology from the M4 GTS.
March 28, 2016: The next generation of BMW M5 has been spotted at the Nürburgring. From the video, it looks like it took some work to get the car tail-happy, which could mean this prototype is all-wheel-drive. Also audible is the twin-turbo V8 which we expect to make 600 horsepower.
February 25, 2016: A new statement to Motoring by BMW M's head of product management suggests that the division is going to keep rear wheel drive for as long as possible. Apparently he feels that the feel of rear wheel drive is central to M cars. This seems contradictory to the use of all wheel drive in BMW's M-branded SUVs, and the on-going rumors of an all-wheel-drive M5. However, it's possible the smaller, lower-powered M cars such as the M2, M3, and M4 will stay rear-drive, while the M5 will get a rear-biased all-wheel-drive system like the SUVs.
July 6, 2015: The boss of BMW's M division revealed some interesting facts about the future of the brand to Autocar. Unfortunately, it seems the days of manual-equipped M cars, and by extension the M5, are numbered, citing the faster shift times and improved fuel economy of dual-clutch transmissions. He also said that as they get closer to 600 horsepower and much more would be "over the limits." This does support the idea that the next M5 will have that much horsepower, but likely not much more. It will also likely send its power to the wheels through a dual-clutch automatic.
June 15, 2015: The next-generation BMW M5 has been caught out testing. The car has massive brakes, low suspension, and larger grilles. The car also features the new model's wider headlights that meet the twin-kidney grille.
January 23, 2015: Just over a week after a BMW employee spoke about the possibility of an all-wheel-drive M5, spy shots come out showing exactly that. The car spotted has a current generation M5 body, but up-close photos reveal half-shafts running to the front wheels. The prototype is most definitely all-wheel-drive, and any implementation would likely come on the next-generation M5, if not just a high-output standard 5 Series.
January 14, 2015: The M5 will have more than just a 600-horsepower engine. According to Auto Express, the super sedan from BMW will also get two more powered wheels. The news outlet reported that a former Audi employee who is now in charge of the BMW M division said that power outputs as high as 600 horsepower might require all wheel drive. However, he added that any implementation would have a strong rear-drive bias.
January 9, 2015: Car magazine reports rumors about the upcoming 5 Series line-up. In addition to a lighter platform, the magazine predicts a variety of new engines. For the next-generation M5, a 600-horsepower engine is expected.