I agree with Fazz.
Considering Twilight Princess was a launch title it sold very well.
Now with a "billion" wiis in households worldwide anything less than 10m will be a surprise.
OoT didn't had the userbase that the wii have.
A good measuring stick will be SMG2. If the second release zooms past the first then zelda should do likewise.
Don't underestimate Nintendo this gen.