Very very exciting stuff. The cover of Blood of Martyrs is a very nice looking piece of new art, too, very cool!
It seems then that the plan is to do a series of "Clanbooks" a bit like the old White Wolf Vampire clanbooks, or even the old D&D Class books. What's interesting to me is the way that FFG seem to mix sourcebook info into every single publication. They don't do "pure" sourcebooks, they do player's guides/adventures that are packed full of background information. I imagine that this wil continue into these "classbooks," so we'll probably see quite a bit of Calixian-specific data on each. That's the stuff I love!
And one would imagine that as these forthcoming books cover Clerics/Scum/Arbites/Guardsmen, we'll probably see similar publications into 2012 for Psykers/Techpriests/Assassins/Sages too...All incredibly exciting.