Nintendo has numerous million sellers this year, but none are on 3DS.

[Asriel]

The sales do seem low, but I wouldn't rule out Samus Returns hitting the 1 million mark. Personally, having been unable to afford a Switch, I've bought a few 3DS titles this year. I've caught up on older games - Alpha Sapphire, Mario Maker (for the single player), Dragon Quest VII - but also bought Dragon Quest VIII, Fire Emblem Echoes: Shadows of Valentia (which I loved) and Metroid: Samus Returns. I might get the Superstar Saga remake and Ultra Sun (I skipped the initial release), too.

Some of it can be explained by mixed reviews - Ever Oasis and Miitopia come to mind. Some of it can be explained by franchise fatigue/limited appeal - which I think is the case with Echoes, I do wonder if the complex release and scope of Fates limited the market for Echoes on 3DS. It's certainly true that my 3DS owning friends (who bought Awakening and Fates) skipped Echoes due to being a little burnt out on Fire Emblem. As for Samus Returns, part of it can be explained by Metroid's limited appeal (1 million sales for a remake would be a good result for this franchise), but it might also be the only title that's really suffered from people buying a Switch. It's Nintendo's absolute core fans who enjoy Metroid, and it's Nintendo's absolute core fans who will be buying the Switch this year.

Overall though I don't think Nintendo will be too concerned. 3DS production costs will be very low by now, and if you look at the 2017 releases, they're a mixture of remakes, upgraded releases, titles made using existing assets/engines, and outsourced games. Add to that ongoing sales from Nintendo's older titles, strong sales from Dragon Quest XI in Japan, and decent hardware sales, and Nintendo's 3DS business is probably chugging along nicely for them. The system is still on track to ship around 5 million for the financial year, which is easy money for Nintendo - even if they just sit back and rely on legacy and third party software sales from 2018 onwards.