"Pikmin 4" is the tentative name for the next main game in the Pikmin series. Not much information is currently known about the project, like its actual name, the console, or the release date. What is known is that it has been mentioned several times in interviews, and said to be in different stages of completion. Because of the conflicting and vague information in them, it is not clear which interviews (if any) refer to the launched fourth title in the series, Hey! Pikmin, and which ones refer to a new Pikmin title.
The following is a compilation of all known official information on the project, sorted chronologically.
Pikmin title possibility and potential
The first mention of a new Pikmin title was on November 6th, 2014, when Shigeru Miyamoto was being interviewed on the recently-released Pikmin Short Movies, during which he said “Continually launching campaigns after the release of software will lay the groundwork for the next iteration of "Pikmin" in the future. And needless to say, we want it to be one of the motivations for potential consumers to purchase Wii U. We are making a variety of different efforts.”, indicating the possibility of that game to launch on the Wii U.
Smosh Games interview
On January 5th, 2015, Smosh Games uploaded an interview with Miyamoto, in which he stated “Well, I wanted to particularly take Pikmin and bring them into sort of that short movie format just because...within the game, we weren't able to really depict the Pikmin individually in the ways that we wanted to. And so, of course, I still have a lot of ideas about what I want to do with Pikmin, but nothing's decided yet. But of course, we will continue to make Pikmin games.”
On September 7th, 2015, Eurogamer unveiled that, in an exclusive interview held in July of 2014, Shigeru Miyamoto once again confirmed the development of the game, and claimed that it was nearing completion. In the same article, Eurogamer also reveals that some Nintendo representatives also spoke to them, and said the following: “We can confirm that Pikmin 4 is in development but that is all we can confirm at present.”. It is not known if the "Pikmin 4" mentioned in that quote is the actual name for the game that Nintendo used, whether it's a placeholder name or not, or if it is just the result of the quote's English translation. The validity of the author of that quote is also not known.
Interestingly, the URL for the Eurogamer interview's page starts with "2014-07-20". Since the URLs of all news article pages on eurogamer.net begin with the article's publication date, this could possibly mean that the article was meant to be revealed shortly after the interview, but was held until September of 2015, presumably when Nintendo authorized the publication.
In an interview uploaded by YOGSCAST Kim, Takashi Tezuka states that “It's consistently Pikmin, but this year it's definitely the fox, the falcon, the rabbit & the frog”, hinting that the company's greatest focus for 2015 is Star Fox, and so, that Pikmin 4 could release at a later year.
On July 7th, 2016, Gamerant interviewed Miyamoto and asked him about the status of the game's development and why there haven't been any news in the past months. To this, he replies “Yes, you are right, and we’re working on [Pikmin 4]. So, you know, when we’re in development we have to create a list of priorities and it has been hard to kind of fit that into that list, but we’re hopefully starting to see that on the list now.”
76th annual general meeting of shareholders
In light of these news, along with the fact that Nintendo was, at the time, allocating nearly all their resources to the Nintendo Switch, it became clear that Pikmin 4's development would have been moved from the Wii U to the Switch.
SoHo Apple Store event
The December 2016 SoHo Apple Store event took place after the reveal of Hey! Pikmin, which happened in September of the same year.
During this event, Shigeru Miyamoto explained how Pikmin isn't as popular as he thinks it should be, and expressed how we wants to work harder on it, along with Star Fox: “Yeah, I always wanted Fox McCloud to be a bit more popular than he is. But I think one more would be Pikmin. So I think these two, I'll need to put some more energy into.”
Second Eurogamer interview
A second interview with Eurogamer was conducted at the E3 2017 showfloor, during which Miyamoto stated “I've been told not to share anything about this from PR...but I can tell you it is progressing...We can confirm that Pikmin 4 is in development but that is all we can confirm at present.”