I think it will sell like SM Galaxy. According to this site, Galaxy released Nov 3, 2007. By first week of January, it sold approx. 4.5 million. That is what I think Odyssey will sell. Approx. 4.5 million.
Odyssey, as a game, is not terribly different from other 3D Mario games. I expect it to sell like other 3D Mario games.
Well, I was dead wrong. It basically doubled Galaxy in the same time frame. Still not sure why people like this so much more than Galaxy. Maybe Super Mario Run is giving people a hunger for more Mario?