It seems that there are new rules for Warhammer 40k inside the box for the new Bloodthirster. Three sets of rules, one for each of the variants. This is an unexpected Development for the release, and could signal how future Greater Daemons will be released for both games as they get released.
Check out the screenshots from someone that got their model early by following the link over to Spikey Bits Forums. I wonder what new book is coming that will have these rules in them for 40k.
The images are from Captain Citadel.