Denpa Men 1 and its sequel came and went on the 3DS, and many folks out there (our own Jonathan Holmes included) enjoyed them. But it appears as if they're still fairly niche sales wise, and a localization of the third entry is still up in the air.
Speaking to Nintendo Everything, Genius Sonority president Manabu Yamana said that he was interested in publishing the third game in North America and Europe -- but if there was ever to be a fourth game, it would have to mix things up this time around. Yamana goes on to say, "If there is to be another [fourth] continuation of The Denpa Men series, I would like to change the game style thoroughly as the first three titles were of the same format and style."
It's rare that you get to see a developer create a trilogy of games in such a short amount of time, and it's great that they've reached this level of scaled success. If it's what they want, hopefully they can find a way to expand the appeal of the series.