9 million is too high I'd say, but 8 million is definitely within reach. I set up my own minimum numbers here for Mario to hit 4 million-selling weeks, my Japan was set very low so 8mil is looking good. I hope supply doesn't get in the way too much for the game's sales!
Still, it'll outsell Super Mario Galaxy by the end of January. So much for the people who thought SMG's sales had anything to do with a 2D Mario!
Also, it'll be the best selling game ever for the month of December, topping Wii Sports' 5.3 million last year.