The information was first reported by Dutch website Autovisie, which also claims that BMW will make an official announcement regarding the car as early as next week.
The most potent M5 at present is the 2014 M5 equipped with a Competition Package. This model has 575 hp as opposed to the stock version’s 560 hp, and will sprint to 62 mph from rest in 4.3 seconds, though it's still slower than rivals. With 600 or more horses on tap, the 30th anniversary M5 should finally be able to fend off the 2014 Mercedes-Benz E63 AMG S- Model and perhaps even the upcoming 2016 Cadillac CTS-V.
Stay tuned for an update.