Let me give you something to think over, I might not be right but who knows? First DLC: Hive Related, Second DLC: Fallen Related. Huge Expansion(technically third): The Taken King(kinda related to the hive). If you think about it like this, we're going to get four small DLC's surrounding each enemy race, the next two small DLC's will be about the Vex And Cabal, I assume. Vex DLC might go more into Atheon and what the Vex have planned for everything or maybe something entirely new. The fourth and final small DLC however, will most likely be centered around the Cabal. Evidence of this? One mission in The Taken King has us set to go look in the crashed Cabal ship and look into the signal that it's transmitting. Towards the end of the mission your ghost states that the transmission was sent to the [b][u]Head Of The Cabal Empire.[/u][/b] This meaning that the message would've been transmitting long enough for whomever was listening to get a good idea of what was happening to the Cabal. Maybe the main head of the Cabal is the raid boss? Lastly, I want to point something out, when your in orbit and a description pops up of whatever planet your heading onto, read it. Venus: [i]The jungles of Venus conceal great treasurers- and terrible power[/i] This is referencing the Vault Of Glass, Moon/Luna: [i]An ancient evil stirs beneath the shattered surface of our moon[/i] This is referencing Crota's End. Finally we have Mars: [i]In the sandswept carcass of a lost city, dark forces gather for war[/i] this description by itself should be referencing the Cabal raid. The Cabal are gathering for a future war that has yet to come, one where the leader of the Cabal empire arrives to gain control over everything and take anything out that stands in its way.