If I had to guess:
Final push for Kirby.They will show one last trailer in antecipation to the launch
Mario tennis Aces will be shown and will be detailed.Both story mode and other modes will be explained and they will say the release date.
Probable push for the Wii U ports too, but most likely wont be given much time.
FE will be shown and given a title name.We will see a CG trailer and hopefully a little taste of how the gameplay is.
Project Octopath traveller will be given its official name and release date.
Other than FE, Nintendo will unveil a new first party game.Either its a big one or more of a "filler" game, its hard to say.But if I had to guess, its a big game that will be teased for the end of the year, and could be the focus of E3, much like Mario Odyssey was revealed.
Outside of that, this will another direct that will have heavy presence of third party games.We will get another batch of third party games, either ports or new games.Indies will also have a presence.
One last prediction that is more bold:Dragon Quest XI will finally appear and we will finally know when the game will come to the west.Square enix wants to double down on the Switch, and knows that the hardware is hot right now, so barring an E3 presence, this is probably the best way to maximize its exposure to the public.