I can't see it being more than ports or probably GC games for the Online subscription service.

I doubt it would be that. That would mean they are going straight from NES games to GC games and skipping everything else in the middle. I am personally of the mindset that if/when Nintendo does bring their GC games over to Switch they will do enhanced HD remakes (think of Twilight Princess HD) and charge between $30-$60 for them depending on the game.

Hopefully Luigi's Mansion is also coming to Switch, seems like such a waste to only release it on 3DS

Well, GBC, GBA and the DS all got a GTA and GTA V is running on previous gen consoles, I don't see them not porting the game over sometime soon.

Shenmue III may be built with PS4 hardware in mind and thus not getting ported. However, the announced HD ports of Shenmue I and II should really also come to Switch, here I don't see a reason why not.

Well, they will have SNes and N64 games as they did before.
GC games would be the real surprise.

Still, i get what you are saying. Too soon!

Remakes aren't out of the question. I just don't think it would be the best option.
If GC games go the way of N64 games on Virtual Console, we shouldn't expect more than 1st party games. So, better save them for pushing the Online service - even creating a new payment plateau to access those games.

I think the question will be: how much appeal they have on today's market? I honestly don't see them having a lot of appeal.
WW has already been remade; MK DD, Luigi's Mansion and Sunshine still don't get a lot of love; Melee? Probably.

So first they make clear that E3 2018 will purely focus on 2018 games. Then they show an ugly ass Fire Emblem game releasing in 2019, but not Yoshi (also releasing in 2019) and a few forgettable ports and indie games releasing in 2018, but they put away other games also releasing in 2018 in a show that's supposed to focus on 2018 games.

Ok.

E3 Direct is just a regular Direct for Nintendo, they dont treat it like a major event for huge announcements anymore, they show off stuff thats right around the corner with a few surprises mixed in just like any Direct.

Last year they had a Direct in September that revealed some new holiday titles, that could happen again this year.

Wont be anything major, those are always known by E3, plus October/November/December are already covered. More Labo kits and 3rd party ports no doubt. Wonder if they're really banking on Labo catching second wind.

Well i do understand that they have form in doing things like this and so it is very possible. But logically i dont see the point of it. Yes you can save some announcements for later but i cant see any advantage to doing so. With E3 you can build up hype for your upcoming games, get a better critical and stock market reception, and showcase more of your games to the world. Saving announcements makes NO SENSE WHATSOEVER. 

A direct this month or maybe a big one in September. Hopefully both.
My guess is more third party announcements and from Nintendo maybe one port or remaster, but I'm not expecting to come later on the year considering MP-Pokemon-Smash is a very big holiday lineup.