Witcher 2 has already proven itself though, so I expect nothing less than stellar reviews for it. It's an excellent game. Alan Wake had too much hype to live up to, and took far too long to develop.
I don't really pay attention to hype, it makes you buy games which are just name brands. I look at reviews and if they are good, even if just on one site, I play the game. Before I did this I missed out on a lot of great games like Chrono Trigger, Pikmin, Too Human, Fire Emblem, and well most niche JRPG's.
Anyway... you make a good point, it will get great scores, but sales are by no means garenteed to be good. I expect only about 1 million sales per console (it will come to PS3), it won't even compare saleswise to Skyrim. I say 1 million because that's about how well Crysis did, and that was a well reviewed PC sequal.