Some rumors I have heard from about 3 different leak sources:
Chapter Approved will:
*Bump all "Cult" Troops to 2 Wounds, claiming this is due to the Cicatrix Maledictum supercharging "the most devoted servants of the Gods". Standard CSM with or without Marks now represent the equivalent of non-Primaris Marines.
*Decrease Mortarion in points -- he's "manifesting more easily".
*Bump "Cult Terminators" to 3 Wounds, with the same explanation -- they gain +1 wound from Terminator armor, and +1 wound for being good boys to their Gods. 3 Wound 'Shroud and Blightlords will be good times.
*Possessed gain Disgustingly Resilient AND +1 WOUND. They are rumored to basically be a weird, "fast" version of Aggressors with no shooting.
*Daemon keyword once again unlocks access to Daemon stratagems (this sounds weird, but could be true.)
*Cultists drop to 4 points per model.
*Poxwalkers drop to 5, and can be taken in squads of 30 or 40 -- rumor just says they increase in squad size and drop in points.
*DisRes becomes nearly army-wide.