Please remember that these are rumors still, and the codex is not out yet. Errors even this late in the game as readers and hobbyists are getting their early versions of the codex could still happen.
via an anonymous source on Faeit 212
the new detachment is called wolves unleashed, which is supposed to be a force of wolves on the hunt. Its basically 6 HQ with everything else standard including the single fortification and lords of war. It does come with two command benefits.
jarls of russ allows you to re-roll your warlord trait
cunning of the wolf allows you before deployment to roll a d6 for each unit. a 6+ and the unit gets outflank. if the unit is a troops unit and has been joined by a ic you get a +2 to that roll. also each turn after 1 you get to choose one unit in reserves, that unit gets to come in with no dice roll