Alphadreams (Mario & Luigi) and Atlus's Etrian Odyssey teams (EO Nexus and Persona Q2 were originally released in 2018) are obvious examples. Nintendo's internal teams that released games in 2017 (Breath of the Wild, MK8D/ARMS, Splatoon 2 and Super Mario Odyssey) will have had three years of development for 2020 titles, so the second wave of major Switch titles is drawing closer. Of course Nintendo will have more games than just Animal Crossing and BotW2 to release in 2020, but they have been in no hurry to make announcements because the rest of 2019 is packed. Bayonetta scores well with critics and the third game should be coming in 2020.
Given that it took most third parties until early 2018 to realize that Switch is a winner, more content from Japanese third parties can be expected in 2020. It's common that games get announced by them only several months before release, so not knowing at this point in time doesn't rule out that 2020 will be a good year.
Alphadream has kind of gotten stale over the years. Their last critical hit that wasn't a remake was Dream Team.
If Atlus were to provide the same support for Switch that they provided to the 3DS, it would easily make Switch the greatest console of all time IMO.
I am worried about whether or not Atlus' EO Team, and especially Alphadream are up to the challenge to making full fledged console style games. To be honest I'm even getting a little nervious about the new Fire Emblem, and Poke'mon.
Pretty sure the Splatoon 2 team is working on Animal Crossing: New Horizons. Right now, I'm looking at 2020 for the Switch, and seeing Bayonetta 3, 75% odds of BotW2, Yokai Watch 4, and New Horizons. If BotW2 gets pushed to 2020, and nothing else new got put out there, then it would be a repeat of 2018, as far as I'm concerned.
But yeah, Nintendo does like to wait until 6 months or less to even announce stuff. I definitely see the potential for a massive 2020 on Switch. But I have to remember that this is Nintendo we are talking about. They've always ran out of gas around year 3 or 4 of a console, or handheld's life cycle. Even if we were to stack and align both libraries of WiiU/3DS together, we would see a slowdown in 1st/2nd party games around the 3rd year.
For Example: 3DS' 3rd year was 2014. Nintendo put out Kirby: Triple Deluxe, Pokemon ORAS, and Smash 4 on 3DS. Wii U's 3rd year was mostly 2015. We got Splatoon, Mario Maker, and Xenoblade X. Poke'mon ORAS was a remake. So the combined 1st party output for the 3rd year of both systems aligned would be Smash 4, Kirby, Splatoon, Mario Maker, and Xenoblade.
Compare that to a combined 2nd year output of 3DS/WiiU...
Bayonetta 2, Tropical Freeze, Captian Toad, Mario Kart 8, Dream Team, Pokemon X/Y, Animal Crossing New Leaf, Luigi's Mansion 2, A Link Between Worlds, and Fire Emblem: Awakening.
And that's if we are going to choose to be generous and give Smash 4 to the 3rd year lineup. If we take Smash 4, and say it's a Wii U game, then it belongs in the 2nd year catagory, which makes it even more lopsided.
If you look at the 2nd year list of the combined WiiU/3DS 1st/2nd party output it looks really similar to 2019. I believe that we are getting that epic 2nd year dump in 2019, the same as if WiiU/3DS were the same system in in their 2nd year. I'm skeptical about 3rd parties ability to move from 3DS to Switch. But again, anything is possible. This is uncharted territory in a lot of ways, and previous years' analysis can only go so far.