I don't think it will sell 6 million.
It would outsell Pokémon Diamond / Pearl Version --------> Doesn't make sense.
I see no reason why not. In ten weeks, B/W managed to sell 4.5 million, whereas in ten weeks, D/P only managed 3.5 million. It is tracking well above the other one, but I guess if the 3ds managed to hurt its sales, then I could possibly see hesitation over whether or not it can pass 6 million.
NOTE: Japan sales only.
"Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth." -My good friend Mark Aurelius