Depends how successful Wii Sports Resort is. I mean Wii might be in a lull right now but so is everything else. But Wii Sports Resort is a huge game that really could set things differently. Not to mention a new Mario game and Wii Fit Plus. If anyone has the big titles coming out this year to expand their sales... it's Nintendo.
But I think a lot of it could deal with how much Nintendo does in Japan. WSR, Punch Out, Monster Hunter 3, NSMB Wii, and Wii Fit Plus could potentially give it a hell of a lot on expanded sales even outweighing the eventual FF13 explosion for PS3.
But if Wii wants to do this by the end of the year, it needs to take off in Japan. It'll get better in America and Europe, but it can really expand that lead in Japan.