I think it will be like condemned, the film where at the end there is a massive guilt trip for the audience.
They put a lot of money into setting it up, they simply wouldn't risk a random error messing the whole thing up by the letting the guy be oblivious to the truth. I think it's funny that when they announced they thought BACTERIA was on the asteroids and no one blinked an eyelid. That would be the most important discovery in the history of science! Also without the main character being an actor it would be impossible to get over legal barriers that would shut the show down. I mean total wipe out had to be filmed outside UK, but letting a man believe his whole world has ended is ok? When the first man first meets the girl, he could have easily just smashed her head against the wall and killed her, the risk is just to high to let a 'Saw' challenge be legal. Still enjoyable an interesting to watch and listen to peoples responses to the program which is ultimately what Derren brown is trying to achieve.