So we all agree the last Pikmin game was Pikmin 3 for the Wii U, then. Pikmin 3 was a great addition to the Pikmin series that was equal parts charming and fun to play. Problem is, it was a Wii U exclusive, so not many people got to experience Pikmin 3 which may become a problem for fans if Pikmin 4 ever gets released.
A lot of people are not going to buy the forth Pikmin if they haven't beaten the previous three, and because of this, rereleasing the third Pikmin game on the Switch would be the best move on Nintendo's part. Even better, bundle it with the first two Pikmin games as 'The Pikmin Trilogy'.
This would be a great way for people who are curious about Pikmin but have never played a Pikmin game to get into the series before Nintendo creates a forth entry (if that ever actually ends up happening).