Reportedly, Nintendo is developing a new entry in the Super Smash Bros. series. This title is not merely a simple port of Super Smash Bros. Ultimate, but rather a full-fledged sequel.
This information comes from the insider Malo932, who has accurately predicted several of Nintendo's upcoming projects in recent months, including a new version of Star Fox, a remake of The Legend of Zelda: Ocarina of Time, and other titles. According to this leaker, a brand-new Super Smash Bros. is in development, but it will not be announced at the upcoming Nintendo Direct, and further details about the game are currently scarce.
Additionally, Malo932 claims that Nintendo is working on new Nintendogs and WarioWare titles, while DLC for Mario Kart World is said to introduce Fox McCloud and launch in 2027. These reports have yet to be officially confirmed.