given that the gatekeepers are highly trained in resisting the AI's persuasive tactics
I'm not sure how you could train people in something like this without actually testing what improves the rate at which people succumb to the arguments of a superhuman AI. If you can't afford to fail even once, how can you judge what will decrease the rate of failure on the real event?
How about fooling both the AI and guinea Gatekeepers into thinking that they can let it out, say, at the push of a big red button which in actual fact does nothing? (Make AI forget about the button by reverting it to an older backup.)
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.