You know, it's sounding more and more likely that this game could outsell Dark Souls 2. Which would be insane. Seems like it's the exact right game at the exact right time in the console life cycle to maximise impact.
1) We have the PS4 which people like to claim "Has no good exclusives"
and yet seems to be selling incredibly well, implying that there is a "thirst" for games to make the purchase worthwhile.
3) The reviews are pretty much unanimous that the game is incredible. Combined with aforementioned "Thirst", more people are likely to go "Oh this is apparently good" and pick it up.
It's like the stars have aligned for them. I legitimately think this game is going to manage 3 million sales over its lifetime, easily.