Its going to be a bit longer than a couple of months, Tal. I haven't even written it yet!
But the plan is to provide new cults, not reprint the existing ones. Further more, I want to explore not just Chaos and Law, but the elemental cults, ancestors, Beast/Plant lords, Sorcerer-Adventurers, and so on. I may include some expansions to cults in the main rules and Bright Shadows, and of course I'll provide new Compulsions and Gifts.
But it'll be a good two months before I begin to write it, so I can't be any more specific at this stage!