Depends on the marketting, but you cant tell yet i guess. Like many said before though, that wii owners dont necessarily buy sequels. However unlike many sequels, this wasnt rushed and its a sequel to one of the best Wii titles. I hope this counts for something, but it probably wont unfortunately. You can definitely count on me buying a copy though

The sequels that Wii owners don't buy usually come within 48-56 weeks after the original, so there is no time for them to let the first game sink in before the sequel is out. Customers are "getting what they want" too soon.

NMH2 is coming 96-110 weeks after the original game, enough time for the audience that bought the 1st to get it and dtermine the userbase. Games like Mario & Sonic at the Olympic Games are still selling great amounts every week, so you cannot immediately drop a sequel to something like that.

NMH1 is selling ~1k a week, so there is pretty much no one else to wait for to get on the bandwagon.

900k is my guess.. The game will sell almost twice as many copies as the original.