I've not been into 40K for long, so this will be my first dance with the WD Codex prance.
This may be a something obvious for the old grognards of 40K, but with GW's current fetish for secrecy, and buying into the rumor that a real codex is/has been in the works, is it likely that the WD Codex will be something altogether alien and divorced from the actual Codex rules being developed? After all, if GW actually is creating a real Codex, this WD Codex could only be seen as a preview ... and we all know how much GW loves giving previews.