Leveling criticism against Splatoon is out of hoping to make the game better because just about everyone who's seen it and/or played it knows that Nintendo is onto something big here. The people who boycott the game over voice chat are, more than likely, going to be in the minority. Plenty of people who have criticized Nintendo's decisions have still expressed interest in the game. There's a general difference between being disappointed with the game's decisions and being completely turned off on it.
But really, Splatoon ought to perform fine. The marketing has been immense, the reception has been overall positive and in terms of support there's not a lot elsewhere to go but up. Nintendo probably estimated the performances fairly when the game originally went into production based on the fact that it is a new IP (one that was originally a lot more low-key) on the Wii U of all consoles. 500k worldwide should be easy to meet and it should be enough to encourage Nintendo to give it another shot in the future on more lucrative hardware.
And in terms of VC it's definitely not too late for Nintendo to add it into friend lobbies which is the only way Nintendo can have it's cake and eat it.