We'd love to post it by next week if we can

No, as far as I know we don't plan to make it a reveal at BlizzCon, though there's a chance the timing of its release could, by coincidence, be around that time. It's still planned to be revealed in the same manner the rest have been -- via a blog on our front page with the visual retrospective of previous tiers and developer description.

We'd love to post it by next week if we can, but I can't promise that with all the BlizzCon preparations taking place.

(The only reason I'm posting right wow po now is because I've been at work for 13 hours today: twitter.com/talkingcongas/status/124695686452228096)

I'll give you a bit of the lowdown on why the death knight set hasn't come out yet, even in the 4.3 PTR files third-party sites are looking through. As with all sets, a concept art piece was done for death knight tier 13. When that was translated to the actual in-game look, we felt it wasn't up to par with the concept, and ultimately wasn't nearly at the quality level of the other tier 13 sets. But, that death knight set was completed weeks ago.