Nintendo’s Japanese support team will stop Wii U repairs. When exactly? When its parts inventory runs out, that determines that.
The Japanese Nintendo Support Page confirmed that Wii U repair components are no longer available. Thus, repair clients must schedule repairs promptly. Nintendo cannot predict when repair support will stop due to supply availability.
Repairs for Wii U accessories like the Gamepad will end when the console does.
The Nintendo Support page only offers repairs for the Switch, Joy-Con, 3DS consoles, Game & Watch (current versions), Mario Kart Live, and the NES and SNES Classic Minis in the West. Wii U repairs have ended.