Animal Crossing + something else. AC sells a lot, but it doesn't get the same love from the media or gamers as say, Zelda or Mario. So I expect next year to be all about AC and something else. Mario Maker 2, the Kirby game, something like that.
On that same note, I expect E3 2018 will be centered around Metroid Prime 4. I can believe that, right?

Animal Crossing.

If Nintendo have a lick of sense, the franchise's HD debut for Switch is already well into production and on track for the second half of next year.

Prime 4 likely won't arrive until 2019 or 2020, and I doubt we'll see Pokemon Switch next year either, given that it's the developer's first HD game.

Pokémon imho

We knew nothing about the Switch lineup for 2017 until January. There's no need to worry.

I completely forgot the most likely to go along with Animal Crossing :

Zelda Maker. And no i'm not joking

I doubt Pokemon will be realeased next year so Animal Crossing. We won't be getting Mario Kart 9 or Mario Maker till the end of the Switch's life in my opinion.

Oh I wasn't aware they denied it. Funny because I fact checked before posting to see if a new Pokemon was slated for 2018 and it didn't say, so I just put the Nintendo quote that it was announced. Sad, I want my Metriod D : 

Animal Crossing sounds most likely out this list ...

Pokemon, Smash Bros and maybe even Prime are a little too early ...

A port (Dragon Quest) and a declining franchise (Yokai Watch) aren't killer apps ...

AC + Pokemon + Smash Deluxe + SMM Deluxe

If you think Dragon Quest XI on Switch won't be a big deal,at least in Japan, you obviously don't know Dragon Quest.

I will give you Yokai is in decline, though it still has enough strength that its first HD entry would move hardware in Japan.

Smash Bros is up in the air, they'll keep that card VERY close to the chest.  Same with Mario Kart 9.