Yo-kai fever has severely diminished in Japan now. Sales of merch are down yet again (last year they were down 75% on the previous year, now they're a similar value). TV show ratings are back down to where Pokémon is. Yo-kai Watch 3 didn't even break 1 million units in its first week. It has since passed, but Yo-kai Watch 2, and even the enhanced version, broke that with ease in the first week.
It's going to be one of the pillars of Japanese games like Dragon Quest and Monster Hunter, but it has lost its edge.