On 15th February 2022 Nintendo announced on Twitter and their support page. That they will be shutting down the ability to purchase games from their eShop for the Wii U console and 3DS handheld family of systems. The planned date for this closure will occur sometime in late March of 2023. Other critical dates include the following which will occur much closer in the near immediate future:
After 23 May 2022 It will no longer be possible to add credit card funds to an account on the Wii U or 3DS systems.
After 29 August 2022 It will no longer be possible to add Nintendo eShop cards to an account via Wii U or 3DS systems. However it will remain possible to redeem download codes into late March of 2023.
This effectively lays out the means by which you can purchase or download digital products for the Wii U or 3DS family of systems going forward till closure. Once these dates have passed. Any potential purchases on these systems will mostly likely restricted to limited means.
For the 3DS family of systems, games can be purchased via a web browser on Nintendo.com. While Wii U will need to utilize the merging of a Nintendo Account to a Nintendo Network ID (Which is needed to purchase via Nintendo.com for Switch & 3DS). Doing this will allow users to add funds via Nintendo.com and then log into the eShop on the Wii U to then buy the purchases they want.
However once late March of 2023 passes. The Wii U and 3DS eShop store fronts will be closed and like with the original Wii eShop. Many of those games will be no longer be available for purchase. Games, purchases like DLC, updates and/or patches, are stated to be available for the foreseeable future. Links listed below.
Nintendo Support | https://en-americas-support.nintendo.com/app/answers/detail/a_id/57847
Nintendo of America’s Tweet | https://twitter.com/NintendoAmerica/status/1493752880733503488?s=20&t=oqCjIo5GFytuXZir86lZnw
As of late March 2023, it will no longer be possible to make Nintendo eShop purchases for the Wii U and the Nintendo 3DS family of systems.— Nintendo of America (@NintendoAmerica) February 16, 2022
More info: https://t.co/uGoxCcDZ70