I wonder if it's just a port/upgraded sequel (like Mario Maker 2 or Metroid Prime Trilogy HD) or just one of their minor IPs since they skipped E3 (Pikmin or Rhythm Heaven)

Probably a couple of new Labo kits to announce.

Offcourse they will, people that think that what Nintendo showed at E3 is hole 2018. lineup are wrong and they completely ignoring how Nintendo managing Switch announcements and releases where in some cases announcing games only around 2 months before launch.
People dont need to expect big games like Pokemon or Smash (they will reamin biggest Switch games of year), but midtier games, some good or big ports/remaster (1st or 3rd party games) are very possible.

For instance, this are games that were announced in September last year, and on right side you can see how much months later they were released:

http://puu.sh/AJM1w/a12df09c4b.png

Well by now Nintendo will know what games are coming out this year. It doesn't make a lot of sense to go to E3 (the biggest platform to announce games around) but save some announcements for later in the year. That does sound like something Nintendo could do but isnt very smart considering the criticism their E3 showing received and the resulting stock drops.

It's like people still haven't come to terms with what Nintendo Directs are for...

Those third parties are never coming back :(

I’m just venting. I wish we’d get red dead2 gta v and shenmue 3. Every other possible announcement will be underwhelming for me.

This essentially confirms that E3 is just not that big of a deal to Nintendo anymore.
It's still important, but not as much as it used to. Shame, but it is what it is.
As for what other new games they might have planned. I also think it'll likely just be more 3rd party ports and remasters or remakes of old games.
With that said, Super Mario Galaxy HD collection please!!!

Well I can see Shenmue 3 and GTAV but I think RDR2 is quite impossible. Maybe too much for the little hybrid to handle.

Then just tell us already

Maybe another labo kit but that's probably it,