Will there be a Mother 4?

The clearest statement came in a November 2015 interview with the Japanese publication Game Watch, given at a Mother event in Japan. Itoi reached for a pop music comparison: among big time pop stars, he said, by the fourth album they cannot make very good songs; the albums sell, but everyone at the concerts wants to hear songs from the first three albums. "When I made 3, I thought I could do it, so I did it," he added. A fourth, he said, was "totally impossible." Pressed in the same conversation, he compared making Mother 4 to running a marathon while holding his breath, and laughed at the recurring American rumor that a fourth game was on its way: that, he said, is simply a rumor.
Nor was 2015 the first refusal. The reference record on Itoi notes, with its own citation to a 2013 Polygon report, that he has said he would not be involved in a fourth title in the series. This Library's Mother 3 shelf carries the same position from another angle: Itoi has stated he has no plans for a fourth game. Three separate points in the record, spread across years, all say the same thing in the same man's voice.
What the record does not contain matters too. Nintendo owns the series and has never announced a fourth game, a remake program, or a successor project, and no statement from Nintendo promises one is coming. A Mother game made by someone else, without Itoi, is not a thing that exists or a thing anyone in authority has proposed on the record. It is a hypothetical, and this page prints it as one.
So the honest answer is a finished trilogy, not a paused one. Itoi's reason is not bitterness and not a dispute: it is an artist's judgment that the third album was the last good one he had in him, delivered, characteristically, as a joke about pop stars and marathons. The series ended the way its author writes everything: on his own timing, in his own words.