As it has been said, the Wii being at the end of its life cycle might be a reason why the sales aren't much higher. So I think there are quite a few people interested in the game but don't have a Wii (any more) and don't want to buy one now any more. So maybe when the Wii U is out, we will see sales figures going up again, especially if Nintendo re-thinks their policy and allows Wii games on the Wii U to be played in HD or at least with anti-aliasing. If a couple of Dolphin developers without source code access can do it, then Nintendo can do it all the more (or do they want to make a quick buck by re-releasing Wii games in HD with just the functionality unlocked?)
