Speculation has run rampant the last few days as the annual announcement of this year's Call of Duty installment prepared for release, with cryptic social-media promotions from developer Infinity Ward seeming to tease everything from another sci-fi inflected sequel to an open world 'persistent shooter' in the vein of Destinyor The Division - with gamers worldwide waiting to see in the medium's defining modern Western franchise would take things in a new direction.