Presumably House of Wolves will partially be set in that big control-tower building in the Rocketyard with all the windows that people were glitching into, right?
Also up in the Citadel on Venus that you ride the big blue tractor beam up into. I forget what the third location was.
There was also the bug that some people found where the locations were already on their star maps, descriptions and all, but access was locked.
And of course all the new items have already been data-mined.
So outside of cutscenes and dialog, and the raid location, people have already found everything in the HoW dlc. Its all already in the game. And, well, seeing as how the Crota dlc didn't have a single cutscene, I'm willing to bet HoW won't have any either. So that really just leaves the raid and some dialog. The dialogue most likely just being a sack of one-liners from another bounty handler. I'd guess even that part is done and its just the raid thats still being tweaked. Pretty lame.
Edit: Oh yeah the raid is in the Reef, and we saw a Reef player hub in a trailer that came out back in 2013, so we know that was also already in development long before the game released too. Assuming its part of this dlc. I'd actually wager that mysterious player-hub is going to be part of the Comet dlc (maybe the hive ship will be located there too).