I predict a fall into obscurity of it. I've not heard of any games as of yet that hasn't really had an equivalent elsewhere (not that the games for it seem to be that much talked about... lol).
There needs to be more "wow, not seen that on the Wii" games for it imo before it can make a dent anywhere. I imagine some people will look at it, look at their Wii, dust off said Wii and use it for a couple of months, before putting it back in the cupboard.
I honestly don't care if it does well or not, but the outlook just doesn't seem promising. Yes, some will sell, but mainly to current Xbox owners I should imagine, rather than new owners.
As many have said, it's most likely too late for it to affect the sales of the Wii in a meaningful manner - everyone I know who talked about getting a Wii now has one. Definitely a case of being late to the party, especially if it's flawed, as World+Dog will be comparing it to the Wii.