I really couldn't even begin to make a prediction I'd be confident with because there are so many variables to consider, at least regarding sales early on.
If Ninty doesn't give the game proper advertising and doesn't bundle the game (basically what happened to DK) then I don't expect a whole lot. That would amount to $299 + $60 for new consumers.
If Ninty advertises well and bundles the game for $299, I think sales will be fairly impressive.
However, if they were to bundle the game and drop the price to $249 (not likely, unfortunately), then sales would be through the roof and likely remain strong throughout the year.