With Nintendo advertising this game almost as well as they did with Mario Kart or Smash Bros, I'm sure this game will do wonderfully well at release, specially for a new IP on a console with a small userbase. Compared with other new IP Nintendo made for the system, the Wonderful 101, this one will certainly won't be a comercial dissapointment.
The Wonderful 101 released in 2013 and sold around 140.000 units that year. Can Splatoon sell more in a month than W101 did in its whole first year?
EDIT: Can you think Splatoon can surpass W101 sales in it first WEEK,or that's too optimistic?