As for "big" releases:
2018 has announced: Fire Emblem, Yoshi, Kirby, Metroid Prime 4 (tentative), and Pokemon (tentative).
I think the conventional wisdom is that we probably aren't seeing the last two next year. The way Pokemon has been talked about sounds like it is probably 2019. The way Metroid Prime 4 was revealed suggests it is further than a year away. But both of these could make it by Nintendo's reckoning; I just don't think we tend to count on them making it.
Other projects that we know/assume they are working on which could be far along: Smash 4DX or 5, Pikmin 4, Animal Crossing, Retro's game, and 2D Mario/Mario Maker.
Nintendo is also trying to create new IP internally. Potentially some such thing surfaces again next year?
As I said on the other place numerous times, I think the centerpiece of next year should be something, perhaps multiple things, among Pokemon, Animal Crossing, and 2D Mario. Nintendo needs to drive adoption, particularly among women, children, and casual Nintendo fans. Mario Kart and Splatoon do some lifting in that regard and 3D Mario does more than Zelda, I imagine, but I think Nintendo has carved out Switch's place as a hot item to their core and has proven that there is space for another dedicated portable system distinct from mobile and the best way to drive the install base now is to turn to less core-oriented franchises. These titles are also, along with Smash, simply their biggest evergreens left: they've done a phenomenal job of getting important, system-driving titles out in the first year.
Kirby and Yoshi are smaller hitters along such lines. Fire Emblem, Metroid Prime 4, Pikmin, and presumably Retro's game could all be used to keep the core engaged through-out the year and drive modest adoption. Smash could be a heavier hitter and help them get their paid online off the ground, as is often said here.
I think a year with Fire Emblem; Kirby; Yoshi; Smash; something(s) among Retro, Pikmin, and Metroid; something, or preferably two things, among Animal Crossing, 2D Mario/Maker, and Pokemon would be the ideal sort of 2018 from Nintendo first party.
The wildcard would be a new IP with the potential to be a Splatoon or a Nintendogs.
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As to mobile, I think Xenoblade 2 is crying out for a gacha spin-off with its blade system, which is a fantasy riff on the system. I think they ought to do Zelda mobile at some point. My best guess is that it is something like Triforce Heroes adapted for mobile: something with multiplayer potential, something loot-driven, something designed around replayability.