According to my source (which cannot be named due to his/her fear of getting in trouble for leaking goodies), the Blood Raven Space Marines will be getting a Codex all of their own for 40K "sometime before 6th edition". Said source insists that Games Workshop has been looking to further capitalize on the excellent sales on the Space Marine range and as such have been grooming the Blood Ravens for the spotlight via the Dawn of War series of computer games.
Apparently the Blood Ravens will get a whole bunch of goodies in order to distance them from the typical Codex Chapters and therefore justify a dedicated Codex - the large number of psykers in the Chapter being one of the main themes. After all, there's already the balanced Chapter (Ultramarines), shooty Chapter (well, sort of at least, in the form of the Dark Angels before their new Codex release and Imperial Fists), and a bunch of close combat focused Chapters (Blood Angels, Black Templars and Space Wolves, to name but a few), so a Chapter that stands out by relying on a large number of Librarians makes sense. Aside from Librarians, the Ravens will apparently make use of some "lost, ancient Imperial Technology" which, coupled with the unprecedented foresight of the Chapter's psykers, will allow many of the units in the army to "begin the game in advantageous positions or receive bonuses".
That's all I've heard so far, but my source informs me that we'll be hearing progressively more about the Blood Ravens, both in further Dawn of War games as well as from the Black Library to prepare the way for the Ravens to arrive in the limelight.
While this may seem fantastic and unlikely, this source is the same that hinted about the addition of the Tau a number of years ago, as well as a contributor to the Planetstrike rumors that we began hearing about over two years ago.
Hopefully this makes for an interesting discussion if nothing else.
Thanks for reading.
Obviously take this with a HUGE grain of salt, but it gives your mind something to nibble on. A very cool rumor, yes, but I really don't want it to happen personally.