Well, one way to take a look at this, is to figure out what armies are being playtested right now. A source very much laid it out, and some of it was quite shocking.
The first thing that stands out when looking at this set is........ Why are Chaos Space Marines listed here. Truth be told, I have no idea, perhaps for a future supplement or expansion? Perhaps it was a mistake that it was listed?
The source itself appears sound for what he knows regarding playtesting, so I am at a loss. I have been unable to get an answer to this, or find out any additional information. Perhaps it is nothing.
Imperial Guard: Whooo hoo. I would love to see a 6th edition revision for this codex. Not only because I play this codex, but it is everyone's ally in 6th. Its release would significantly effect many different codices.
Before I go too far on what I think of this, here is the rumor bit. Please remember that rumors always require the use of some salt.
via an anonymous source
I wanted to email you, as I saw you post some Ork rumors the otherday. I did not send those rumors out, but I can confirm somewhat their accuracy. There has been a lot of playtesting Orks vs. Marines, vs. Tyranids, and vs. Tau. Iknow there is another group doing Eldar, IG, Black Templar, and Chaos Space Marines.