Yea I think the 4-5 million projections for Japan sales of NSMB Wii will probably be pretty good. As for worldwide, I don't doubt it being a huge seller for many months to come. U.S. sales are going to be hot for quite sometime. I'm telling ya, this is getting new, young, old, and veteran gamers all alike to pick this title up. Considering how big the NES and Mario was in America, I think this can sell huge numbers for a long time there. Game will definitely have Mario Kart Wii type sales trends but potentially at a higher magnitude.
Only region that may potentially have issues is the European areas, namely the UK. I think the rest of Europe, especially France and Germany, will continue to have long sales trends but the UK may be a little different. But we'll see how it sales there over time.
I'd say 15 million right now is an easy projection for this game to hit and 20 million is probably likely for the title. Just going to be curious how this title sells along with Super Mario Galaxy 2, but it is Mario and people will pick up both more than likely. This game is going to be fun to watch over the next 12 months.