10m would be bold enough already, beating the previous record by ~2m. 12m is pretty bonkers.
The game is certainly selling at a staggering pace, but the question of the saturation point is an important one. Pokémon was a phenomenon back in the day and ultimately had its legs cut short with the altered releases of Blue and especially Yellow, so 10m for a game in Japan is within the realms of possibility. But 12m? That's certainly more tbone-ish than a few other of your predictions lately, so I'll give it to you that you've been getting back in the groove.
Best-selling game of all time in Japan: Yes.
10m lifetime: Maybe. I am 50/50 on that one because the first several weeks had amazing sales.
12m lifetime: Nope.