I hope it sells like ape-shit but the real uphill battle for it is the install base for the ps3.
I just can't imagine that more than 1 in 4 playstation owners will buy it - the tastes are waaay to varied and not everybody loves RPGs.
So lets say that the install base is 20 million when it comes out - the most I think we could expect would be 5 million in sales (25 million PS3s - 6 million) I think that's a reasonable expectation.