1 or 2 of these may not show up but:
1. marvel ultimate alliance 3
2. link's awakening
3. fire emblem three houses
4. mario maker 2
5. pokemon sw/sh
6. luigi's mansion 3
7. animal crossing
8. dragon quest 11 S (maybe a reminder for DQB2 as well)
9. astral chain
10. daemon x machina
This is a dangerous prediction, but I actually wonder if a few of these might not be shown.
Fire Emblem and Daemon x Machina both got a trailer last E3 and an in depth look during the February Direct, so I wonder if they might be relegated to the Treehouse this time around.
They might also save Link's Awakening for an August/September Direct if it's coming out very late in the year.
Dragon Quest XIS also got a pretty deep dive in February.
I'd say there might be a chance that MUA3 or Super Mario Maker 2 get skipped too, but the Marvel brand is probably too big to ignore and Nintendo has been explicit about there still being surprises left to reveal for SMM.