So, probably speculating way to0 early in the course the game (heck - I'll admit I have barely dug into the storyline and bounties) to ask, but... -The main game has revolved about the Vex and the Dark Heart. -The first DLC dealt with the The Hive minions and their god-king, Crota. -HOW is dealing with the Fallen in more detail, plus adding more information about the Awoken, and some smaller implications about the Tower politics. So, it would make sense that the next DLC or whatever it will be deals with Mars and the Cabal, right? They've been pretty much stock villains/roadblocks for the most part this year. So I would assume they are going to expand on that - maybe a Cabal invasion force in the wake of all the chaos across the system with Wolves' uprising and the Awoken distracted by it. Just speculating for now; way too early to say for sure I guess.