I think the massive holiday/ black Friday sales just recently should prove as a lesson that the Wii is nowhere near done with selling. To not reach 100 million, sales would have to almost COMPLETELY implode after the holiday season. It would practically require NO more games to be released, no future price drops, and a new Nintendo console released prematurely, and even then, it could inch its way there merely on the strength of older titles.
At least 80 million is essentially guaranteed by the end of the holiday. So bascially anyone that doesn't think the Wii will reach 100 million is saying that from January 1st 2011 until, well.. forever, Wii will not be able to sell an additional 20 million units. Even during holiday 2011 alone, it should sell at least 1/4th of that amount. Wii still has more bundles, at least two $50 price drops, Vitality Sensor, and more motion plus software, including the big one, Zelda.
Now, will Wii outsell the PS2? That's an entirely different story. I don't think it will, but it will be closer than most people think. The problem is that Sony has two key advantages with its console that Wii does not have. One is major third party support, and the other being people rebuying PS2s either because of broken ones or the slimline. Wii should easilly outsell the PS1 though, which has sold just over 100 million.
I think lifetime sales of the Wii will be anywhere from 110 million - 130 million depending on when Nintendo decides to release their next console.
