It would not surprise me at all if this whole issue is being kept in reserve until the election looms closer. At that point, the burden of truth (at least in the eyes of the public) will shift to the accused, at which point a cornered politician might feel he has no choice but to claim executive privilege.
Which, in the eyes of the general public, would be an admission of guilt.
Of course, that cheapens the entire issue and the underlying tragedy, but that's the way things go in politics.
I won't deny the possibility/plausibility of this scenario. I disagree with it, but that's of little importance. What I think IS important is that our so-called "friends" in Congress trade so casually in the defense of our rights. And their "friendship", for the most part, rests solely on today's, tomorrow's, next week's, whenever's polls.