Scott has stated he has a responsibility to the studio and that Tom Rothman is pushing for PG-13/12A, scott has stated he has shot a hard cut and a PG-13/12A cut of the film. It's not just blood and gore or profanity which lead to the final rating it's the tone alongside the intensity too. Tom Rothman and his execs will visit the set during production, and if they want something painted lighter or a certain feature obscured, so it appears more family friendly, they can demand set changes as they did with xmen origins wolverine, because they're worried it won't apply to the masses or give the ratings board a headache, if fox are pushing for a PG-13/12A. What i'm saying is it wouldn't be that difficult to tone the film down from an R/15 to a PG13/12A, digitally remove the blood/gore (even though Lindeloff has stated prometheous will not be as gory as the alien films), edit out the nastiest scenes or shorten them, and take out the nastiest profanity, it's not that difficult to do, and i wouldn't be surprised if they spring us with the PG-13/12A surprise very soon. But believe me, i would much prefer to see a harder cut in the cinemas of prometheus, so fingers crossed and let's see what happens.