Today Nintendo announced that eShop support for Wii U and 3DS platforms will be discontinued as of March 2023. This will have a ripple effect throughout all Nintendo properties, but for Fire Emblem it will have several unfortunate consequences.
Thanks to Twitter user @GC1_5, for catching this; As of May 23, 2022, You will not be able to add funds using your credit or debit cards to your Nintendo eShop account for the Wii U or 3DS. Additionally, as of August 29, 2022, you will not be able to add funds using Nintendo eShop Cards to your Nintendo eShop account for the Wii U or 3DS.
As for everything specifically that will be lost to time, read below: