This is according to an interview that Nintendo of America’s President Reggie Fils-Aime did with Polygon. According to Fils-Aime, “From a first-party standpoint, there’s no new development coming after the launch of the legend of Zelda: Breath of the Wild. We really are at the end of life for Wii U.”
Note that Fils-Aime states that it will be the last first-party title, meaning that there is a possibility that other third-party developers could still have games for the Wii U in the works, although like we said given that the console’s production is said to end soon, it doesn’t make sense for developers to create games for it anymore.
As for sunsetting, Fils-Aime states that it will be awhile before that happens. “From our standpoint, sunsetting is quite some time into the future. The ongoing activity from an online standpoint on [Mario] Kart and Splatoon is significant. We’re going to continue to support that.”