I suspect bluff. The damaging revelations about surveillance are already done, unless he has document suggesting Putin is a CIA operative or the notorious Chinese hackers actually work for NSA, or has recording of Obama ordering assassination of Tea Party leaders, or something of that measure of insanity - I don't see what else could he reveal. By now everybody is pretty much sure NSA owns phone networks (at least in the USA) and the Internet (pretty much anywhere) and gets unreserved cooperation from every major provider. What else could there be?