Here's a doozy. Fluff changes. (prepare for heavy summary) We're moving on from the 41st millenium into the 42nd. Yup. Here's the rumor: mankind's days are really waning. They're heading down the crapper fast and xenos, especially Necrons, are coming into quite the threat. Well, mankind just doesn't have the power, and now Necrons are threatening Chaos, and the Chaos forces are like 'well wtf guyz'. So, Chaos has to fight across the galaxy against the enemies that mankind were fighting against, perhaps even allying with loyalist forces against a common foe. This will be expanded on in the coming Codices, including Necron and Chaos Legions, which should set up for the big fluff change in 6th edition. Some of the rest sounded more like wish, opinion, and extrapolation; Void Dragon coming up, Primarchs coming back, Emperor's descendants being found by an unnamed portion of the Imperium in order to fight the Void Dragon, etc etc...