Raiders seem like an obvious choice given the coaching staff being already primed for sound bite heaven, a rebuilt team that features one of the more colorful/polarizing players in AB, a fresh and numerous stable of high draft round rooks, and an iconic historical team in their last year in Oakland.
As a Raider fan, as much as I'd love the peek inside, I hope they don't do it because one added distraction - a media-circus-sized one to boot - is the last thing this team needs.
I also think it's improbable as the Raiders have always been a notoriously private club, historically closing even their practices to the press. That's an artifact of Al Davis, and Gruden/Mayock may crave the limelight in a way Al and the staff he brought on did not, so its possible the new culture would have no issues with being on Hard Knocks.
Again, I hope they stick with tradition and don't do it.
So my bet is actually on the Giants as well. As
@Hankmoody says, there are a lot of story-lines: the pass-the-torch and/or who's the starter tension b/w Eli and Jones, a marketable player the fantasy community will definitely want to tune in to see, a few intriguing rookies of their own, and a big market audience.