Yes the game will have big legs

If they bundle it, possible even with an Amiibo or two and a lot of marketing I reckon it could go towards 2-3m even.

I'm hoping it at least reaches 4m because it looks like such an exciting fresh take on shooter genre.

It needs to be marketed, then it will do fine. Market it as Mario Kart with paint guns and I think it will crack a million easily enough. Stellar reviews will help as well.

Call me a pessimist, but I'm a bit concerned about reviews. I can see it losing a lot of points for no voice chat, the number of maps/modes, and local multiplayer only being 1v1. I'm expecting a Metacritic in the high 70s.

Easily it will probably do 1.5M by xmas

I agree with this. I heard Splatoon amiibo are selling out quick too. Not sure if that's just scalpers but it's probably a good sign.

Even Captain Toad got 81% lol.

All previews have been super optimistic.

Mario Kart 8 got 88% despite having a terrible battle mode (and only 2 modes in total).

Most of the previews were pretty good though. I expect low-mid 80s. Probably 83-85. 

Captain Toad is amazing. :P

In all seriousness though, I hope you're right, I can just see the game taking a hit in reviews and this impacting sales negatively. I don't want Nintendo to be discouraged from trying new IPs.

I doubt it, i think 900k max in 2 years. But it will be profitable like other nintendo games