Over a year ago, Nintendo's Shigeru Miyamoto revealed that Pikmin 4 is nearly complete, but Nintendo went silent for many months afterwards. This past July, Miyamoto gave an update on the project, indicating that it had slipped off of Nintendo's list of priorities but that development would hopefully resume again soon. There's been no official word since then, but according to the latest leak from Laura Kate Dale of Let's Play Video Games, the game has undergone a significant change.
Dale recently tweeted out tweeted out a rough outline of Nintendo Switch's planned software support based both on official information and unofficial leaks via her trusted sources. According to that list, Pikmin 4 is no longer Pikmin 4 at all, but a reboot. According to Dale's schedule, this new Pikmin title is planned to launch sometime in Autumn 2017.
I've chosen to mark this story as a rumor (rather than marking it as a "Report," as we usually do with Dale's scoops) because we don't have the usual clarity regarding her sources. Dale has sources at Nintendo and Ubisoft who have repeatedly proven accurate regarding stories like when the Switch reveal would take place, the content of the reveal, Switch's use of cartridges, and the design of Nintendo Switch's portable unit.
However, Dale states that some of the information in her Nintendo Switch software schedule only has a single source and that some of the information differs from what other leakers have heard. I've reached out to see if she can confirm that this latest Pikmin story comes from one of the sources that has been proven correct before, but I haven't received clarification at this time. I don't expect elaboration, as Dale has to prioritize protecting the identities of her sources.