That is truly difficult to say. On the one hand; there aren't really a lot of good titles to compete for gamers' attention on the PS4 right now but on the other hand; it is a tad foolish to assume that every single PS3 owner who owned and enjoyed the two first ones would suddenly make the 8th gen jump due to this one title, it's a big investment and it is equally unlikely that a game with a fairly peculiar premise will draw in vast amounts of new fans as well.

It's a complete joker from where I'm sitting, could range from 1 million to 3.5 million but I find both equally unlikely and will settle somewhere near the middle for the sake of sheer balance on my own part. I'll guess somewhere between 1.75-2.5 million (I'm leaning more towards slightly shy of 2 million though, we also have to consider that, traditionally, this is not a hugely favorable time of year for game releases), should be possible since there are already five million sellers on the platform and four of them are multiplatform, a good quality exclusive should do quite well.