If the gatekeepers are evaluating the output of the AI and deciding whether or not to let the AI out, it seems trivial to say that there is something they could see that would cause them to let the AI out.
If the gatekeepers are simply playing a suitably high-stakes game where they lose iff they say they lose, I think that no AI ever could beat a trained rationalist.
Update 2013-09-05.
I have since played two more AI box experiments after this one, winning both.
Update 2013-12-30:
I have lost two more AI box experiments, and won two more. Current Record is 3 Wins, 3 Losses.