It's Finally happening! Check out the article right from Halo Waypoint:
Grab your controller and prepare for the Flood; Halo: Spartan Assault is poised to storm living rooms around the world this holiday! Today, 343 Industries in conjunction with Vanguard Games announced that Halo: Spartan Assault will be available worldwide for digital download this December for both Xbox One and Xbox 360.
Halo: Spartan Assault for Xbox One and Xbox 360 will pit gamers in a galactic-scale war against a persistent and overwhelming enemy from long ago – the Flood. With over 30 stimulating missions at your fingertips, play longer than ever with the all-new online Co-op mode and the Operation Hydra expansion that delivered an action-packed addition to the single player campaign.
Will you be getting it? If so are you gonna buy it on the 360 or wait and get it on Xbox One?
EDIT: Ok, I've found the features coming that are exclusive to the console version of Halo: Spartan Assault.
Play longer than ever in a new online Co-op mode, and watch each other's backs with all-new Co-op missions*