Agreed. Companies would try to give at least like a minimum 6 months reveal before release for proper marketing and build up of their game/product. 

If anything were to be released for Nintendo before the end of this year/holiday I would expect them to show something before the end of July at the latest.

Well, I was asking for the entire second half , so pretty much anything coming out this summer and fall from Nintendo apart from Paper Mario. In 4 months summer will be over and we'll have all the answers already.

I'm hoping Snap comes ASAP, but feel like that will be a September-early October game.

Pokemon's going to be the big holiday game again this year, not just Snap, but New Pokemon Colosseum/Let's Go Johto too.

Q3 - New Pokemon Snap, Wii/WiiU Remaster/Collection (3D Mario, Metroid Prime, etc)

Q4 - Pokemon Let's Go 2, Bayonetta 3, Super Mario Party 2

Nothing stellar, but still enough to shift millions of software sales.

July : Paper Mario (obv)
Aug : Pikmin 3, Pokémon snap
September : Metroid Prime Trilogy
October : Mario collection
November : Bayonetta 3 ?
December : Pokemon CT DLC

It's hard to predict specific games.  I probably wouldn't have guessed Paper Mario and Pokemon Snap were on their way until these games were announced.  Overall, I think they will have 1 big holiday game plus 3-4 small to medium sized games after Paper Mario's release.  What these games are I don't really know.

In some ways, holding botw2 until next year actually makes smarter business sense even if it is ready for this holiday. Ps5/XSX launches are going to take up a lot of attention. Might be better to have botw2 somewhere where it can dominate the zeitgeist all on its own, like March

Not only that, but it would be Zelda's 35th next year. I feel like the Switch can keep its insane momentum with a heavy hitter around March and another for the holidays. It worked for 2017's launch, it is working for this year with Animal Crossing. It would be really great to see if they can keep this up. 

I just hope they have a system seller for the holidays. I don't think Let's Go Johto would cut it. I'm starting to wish for a new Mario Kart... I know it's unlikely because of the way 8 is selling like crazy. 

I am not expecting MP4 this year, as development was restarted on it late 2018 as far as I remember. I do hope that the sequel to Breath of the Wild will be out. Really liked the vibe of the teaser, and with a ready-to-go engine and game world, I think it should be doable.
Ports of Pikmin 3 and Super Mario 3D World should also appear IMO, and maybe a MP Trilogy re-release as well. Fingers crossed!

A Paper Mario I was expecting, but not for this year, only next year. I thought hey'd need longer to make one after color splash.

Pokemon Snap however has caught me completely by surprise. With announcements like this, who really knows what can come in the next months?

But I doubt any of those to happen, especially the last one.