I think it'll be lucky to reach a million. The type of people that own PS3s aren't gonna be into this kind of game. You'll get a vocal minority praising it but the masses will be like, "it's not a shooter and it's not violent as hell, no thanks." Meanwhile a soccer mom or an older Wii owner would probably look at it like, "oh, it's an interactive murder mystery, that sounds interesting"... but it's not on the Wii.
On top of all of that, I doubt the people in charge will market this to the huge audience who would be interested. All the ads will probably be on gaming sites where the bulk of people could care less. They need to hit places where adults will look, but they won't. They won't even think about advertising it there and it's a shame.
