To be fair, on the day of E3 2017 Miyamoto was asked about Pikmin 4 again after Hey Pikmin was already revealed in April that year and due to release in July; he said it was progressing. Personally I think Hey Pikmin really is a different game, and Pikmin 4 is just stuck in dev heck. Hey Pikmin was made by a different team too, and Pikmin very likely just doesn’t get prioritized.
Of course, Miyamoto could’ve just used weird wording I guess, but it’s not really
‘d to see how he could’ve really meant the next mainline title.