But Chaos clearly IS in the game, it's what the trailer was all about! I assume instead of making them a playable faction they are the bigbad in the game and in doing so they can do things that had they been a playable faction would make it unbalanced. Like giant boss battles and incredibly huge strongholds.
I assume each of the 3 games will add at least 4 new playable factions, which means at least 12 when all is said and done. I am hoping they all use the same base map, maybe expand on it each game. So by the end you have a full map of the world, full on incredibly deep playable factions.