what are the reasons that make march a "quiet" month
December and January are the Christmas/Post-Christmas Rush, where people have mad amounts of money to just BURN through content, hence the epic amount of releases in November/December to lead up to the big few sales days.
February through to May therefore suffer as people are still recovering their wallets and probably have a stack of games still on the backburner to get through. Historically (and it appears Nintendo have been quite smart about taking advantage of this, the cunning bastards), these are months typically used to clear games that companies aren't as comfortable about thanks to the reduced competition, where slow numbers are anticipated.
June down to August are "preview periods", where games can get really good publicity. This is a fantastic period to smash games out because of the End of Financial Year (it gets your chequebooks in the green), but also if you take advantage of the open marketing, you can get some fantastic expose, and people are more likely to purchase something fresh in their mind than something from a while back.
September and October generally also get a bum rush like the Post-Christmas period as it's right before the major holiday season. Go too early and your game will get swamped by the new releases as people start doing their shopping.
I don't think the planned release suggests a lack of confidence, however. I think it's an extremely smart plan for longevity. They don't want a sudden, giant cash boom and then nothing; they want a slow trickle of profit to keep their financial data solid for the next couple of quarters. Selling it in the slowest section of the year is a brilliant move as it basically means Nintendo has no dangerous competition to deal with; Project Scorpio is still far off and the PS4 Pro and Xbox One S have already made their major sales dent.
The Nintendo guys know what they're doing.
