Okay someone posted a query about this on a Facebook 40k group, as they found a listing online for a new novel by Dan Abnett, due out in Jan 2016. Named "I Am Slaughter" it has the following synopsis:
Sounds like an interesting novel set in the aftermath of the Heresy and the Scouring that followed it.As the greatest Ork Waaagh! ever seen threatens to engulf the galaxy, the Imperial Fists make their last stand
It is the thirty-second millennium and the Imperium is at peace. The Traitor Legions of Chaos are but a distant memory and the many alien races that have long plagued mankind are held in check by the Space Marines. When a mission to exterminate one such xenos breed on the world of Ardamantua draws in more of their forces, the Imperial Fists abandon the walls of Terra for the first time in more than a thousand years. And when another, greater, foe strikes, even the heroic sons of Rogal Dorn may be powerless against it. The Beast Arises… and it is mighty.