It'll be the best selling Persona that's for sure. It's really gained a lot of exposure and more fans since Persona 4 Golden. I'd never even heard of the series before that title released.
1.5 million is possible.
Persona 4 Golden is my singleplayer game of the generation so far. I can't really say game of the generation because I can't compare Persona 4 and Mario Kart 8. Mario Kart 8 is my multiplayer game of the generation so far.