It seems that Activision and Platinum Games have up until now managed to hide the fact they are working on an M-rated Teenage Mutant Ninja Turtles game. Platinum Games are known for developing games as Bayonetta, Metal Gear Rising: Revengeance and the recently released Transformers: Devastation.
The game is being released on PC, as well as last-gen and next-gen consoles, according to the Brazilian ratings board. The Australian ratings board states the game has very mild impact with language and moderate impact with violence; an Australian M rating may be a Teen rating elsewhere.
No word yet from the American ESRB or the European PEGI, so stay tuned.