From Pete Hines' Twitter:
We have not announced Dawnguard for any other platform, nor given a timeline for any such news. If we have news, I promise I'd tell you.
Yeah, it's not coming anytime soon.
In all likelihood the exclusivity period didnt start until the non english version's of the DLC were released, which if I remember means that the exclusivity period would end August 10th?
I seriously doubt that, actually. After nearly 30 days of radio silence it's pretty clear that "do not talk about other releases" was a part of the deal. I don't think it's a coincidence that they've started talking now, even if it's to say absolutely nothing.