Nintendo’s Japanese support has announced that they will end support for repairs for the Wii U. When exactly? Well, that really depends on when the current stock of parts runs out.
The press release was published on Japanese support site for Nintendo, confirming that the retention period for Wii U repair parts has passed. As such, customers in need of repairs will need to book sooner rather than later. Nintendo cannot provide guidance on when support for the repair will end as it depends on remaining stock.
As for Wii U accessories (ie Gamepad, etc.), repairs for these will end at the same time as the main console unit.
For those in the west, Wii U fixes have already stopped, and the only options available on Nintendo’s support page are for Switch, Joy-Con, 3DS consoles, Game & Watch (modern versions), Mario Kart Live, and NES and SNES Classic Minis.