The online service of 3DS/Wii U will be terminated on April 9th. Pokemon Bank and PokéMover will continue to be available online. Passing communication can also be used for local communication.

The online service of 3DS/Wii U will be terminated on April 9th. Pokemon Bank and PokéMover will continue to be available online. Passing communication can also be used for local communication.
The Nintendo 3DS/Wii U software online service will end at 9 a.m. on April 9, 2024....

The linked article is in Japanese.