The release won't happen until after 1.7, I highly suspect 1.7 has many undocumented fixes for things that came up with the Xbox version of Dawnguard that are Dawnguard specific.
What irrates me most is probably how long they waited to roll out the 1.7 beta patch, because as long as it is in beta we won't see hide nor hair of Dawnguard, and if it isn't a fixed period beta then we may not even see a release date anytime soon.
Having a release date will calm a few people down, there will still be a lot of annoyed people but it is better than everyone being annoyed that the exclusivity is up and they are still in the dark.
I think I speak for everyone on PC when I say, "I CAN FIX IT MYSELF I WANT THE DLC NOW"
Seriously though we have 1.6 which has the necessary code for the whole dlc, so all we need is the dlc, please give it to me now, I dont want to wait for your.........."fix".
I can and will do it myself.