With the end of the year coming, time to wonder for the next. 

The known titles are Brian Training, SMT x FE, and Animal Crossing. 

The titles we know are real are Bayonetta 3, Metroid Prime 4, and Zelda BOTW 2. 

....Can't see Metroid, and for all the rumors I'm not sure on BOTW 2. So....what else is there? 

A Pokemon title is likely...but what else?

I honestly have no idea, but that excites me. Did we know more about 2019's lineup at this point last year compared to what we know of 2020? I feel like we knew of a lot more... Luigi's Mansion, core Pokemon (we knew it was coming, just not Sword and Shield), Fire Emblem, NSMBUD, Yoshi. Maybe that was it...

I think BotW 2 has a slim chance of seeing a 2020 release. Nintendo has plans to release it in 2020, but I doubt it will make it on time without delays. 

Animal Crossing will definitely launch in 2020. 

I'm happy so long as I get my 4 good Nintendo exclusives a year. So far Nintendo is averaging 5 good games a year. 

2017 

BotW
Mario X Rabbids
Xenoblade 2
Odyssey
Splatoon 2

2018 

Let's Go Evee/Pikachu
Smash Ultimate
Xenoblade 2 Torna

2019 

Yoshi's Crafted World
Mario Maker 2
Fire Emblem Three Houses
Astral Chain
Luigi's Mansion 3
Link's Awakening
Poke'mon Sw/Sh

So the way I see it Nintendo is currently 3 games ahead of the 4 game average curve that I prefer. So they could afford to make 2020 a year with only three good games like 2018 was, and they'd be fine IMO. 

Nintendo announced a new game by the Odyssey team? 

Any news on Splatoon 3? I read that there are rumours about it being in development already.

I swear to God if Nintendo manages to put out BotW2 and Odyssey 2 within Switch's lifetime I'll just call it the greatest console of all time. Having both Galaxy 1 and Galaxy 2 on the Wii was crazy enough. 

So the confirmed 2020 titles we have are bellow. :)

January Brain Training For Nintendo Switch EU release
January Tokyo Mirage Sessions #Fe Encore
February ?
March Animal Crossing: New Horizons
Then April to December to fill!

And three games annouced for 2020.
Famicom Tantei Club: Kieta Koukeisha Remake
Famicom Tantei Club Part II: Ushiro ni Tatsu Shoujo Remake
Xenoblade Chronicles: Definitive Edition

Confirmed by no one:

Banjo and Kazooie Three
Goldeneye 2
Super Smash Bros. RPG open world game
Paper Mario: Return to the Thousand Year Door
Starfox Adventures 2
Sonic Adventures 3
Yoshi's Story 2
Advanced Wars Sequel
Diddy Kong Racing 2
Starfox AAA sequel
Donkey Kong 64 Sequel
Metroid + Rabbids: Galatic Battle
Star Wars: Rogue Squadron 4
Runescape 4.0 (exclusive to Switch)
Exclusive Diablo 3 expansion (the art style is more kid friendly than D4, as is the storytelling)
Hyrule: Total War released on Switch and PC
AAA Narnia game exclusive on Switch

The next 3D Mario game after Odyssey is likely to release next year. More than Breath of the Wild 2, in my view.

Here are some things we might see in 2020.

1) The usual suspects - games that regularly come out on handheld or home consoles.

Wario game (either platformer or smooth moves)
Mario RPG
Pokemon Mystery Dungeon (or other Pokemon spinoff)
Proper 2D Mario game (non-port or non-Maker)
Proper Donkey Kong Country (non-port)
Bayonetta 3
Metroid Prime 4
Tomodachi
Nintendogs
2D Metroid
various Mario Sports titles

2) Revive old franchises

Advance Wars
Punch Out
F-Zero
Starfox
Excitetruck/bots
Wii Sports (or something like it)
Kid Icarus
Golden Sun
Star Fox

Lots of others.  Too many to count.

3) Ports & Remakes

There are still a few Wii U games left to port.  On top of that we got Link's Awakening this year and Xenoblade Chronicles is on the way.  Nintendo will likely have at least one other port in 2020 either from the Wii U or an older console.

4) 3rd Party games using Nintendo IP

The Switch already has Mario + Rabbids, Hyrule Warriors, Fire Emblem Warriors, Starlink (w/ Starfox content), and Cadence of Hyrule.  They are showing that they are actively trying to get 3rd parties to make exclusives for Switch using Nintendo IP.  I doubt this is going to stop. 

5) Sequels

Pokemon, Mario Party and Kirby sequels are definitely going to come eventually (though not necessarily in 2020), and we already know about BotW.  Mario Odyssey, Mario Kart, and Splatoon are all games that may or may not get another game on the Switch.  Also, while technically a Square Enix game, I know the Octopath Traveler team is working on a sequel or some game like it.

6) New IP

So far we've gotten ARMS, Snipperclips, 1-2 Switch, LABO, and Ring Fit Adventure.  (I may have forgotten a game.)  Nintendo is putting out at least one new IP a year.  I would not be surprised to see this rate increase either considering how successful the Switch is.  Nintendo can afford to be more experimental at this point.

In short, Nintendo has a lot of games that they can still release including several heavy hitters.  They are in no shortage of potential content.  This is not even counting the release of 3rd party content, which has been accelerating each year.  And the Switch is successful enough that Nintendo can take some risks starting new IP or resurrecting old IP.  In fact, I think it is very likely we will see at least one game from each of the categories I listed.