So I think there's a bit to just point out here.
Partner Showcases are probably a thing because Nintendo isn't developing those games. They are made outside of Nintendo, which means that those devs are more easily able to identify release dates and everything else.
Nintendo first party titles have been announced by Twitter. This is probably because they don't want to commit to release dates in case they can't make good on them. This is clear through Paper Mario and Pikmin 3.
That said, Smash is developed externally which means that any upcoming presentation will probably be on schedule and simply not reveal the character beforehand. Think like the Byleth presentation. With Min Min having her presentation done in May, presented in June, chances are the presentation itself is done.
All this means is, first party titles will probably be announced separately, Partner Directs are easier to work on due to Nintendo itself not having commitment issues to release dates, and Smash is probably on track, but isn't revealed until just before release.
EDIT: Smash development usually works in groups of 3, meaning 3 are usually worked on at a time. Min Min and two others were worked on, meaning now picks 7-9 are in the works. 7 is, probably, close to being done. Doesn't mean a reveal is imminent, but I don't know that we'd be waiting until October.
That's my thought process anyway. What do you think?