Easy to disseminate an online PDF like they already have(not) done for the SoB WD codex?Uhm, in the 5th ed book, Sisters got a larger entry than grey knights did. Seriously, they aren't going to get forgotten. Given how long they've been working on this, I would be amazed if there isn't something prepared for release day that tugs all the older codeces in line. They've done it before, they can do it again. Back then it wasn't as easy as now, either, what with online PDFs being so easy to disseminate...
The 5th ed BRB virtually retconned the SoB out of existence save for a couple paragraphs and mention in "Forces of the Imperium". I remember buying it on release years back, cracking it open with my friends and feeling the huge sigh of disappointment as the 1000$ in models I had sitting on the shelf barely got a mention.
But maybe you are right. Maybe they didn't release the PDF because they are planning to come out with a full codex soon. Maybe come 6th ed, every army will be promptly updated with online PDFs. Maybe every army will be able to field flyers and many older Codex won't have useless, redundant, and outdated rules. Maybe each army will have a full fluff and art section in the big rulebook and some new official artwork will be released for the SoB. Maybe GW will have sanctioned tournaments in the USA again and offer prize support for licensed FLGS for events, leagues and tournaments.
Maybe GW will get bought out by WotC and all that will happen. Until then I'm not holding my breath. :smoke: