Nintendo is ending online play services for both the 3DS and Wii U on 8th April, the company confirmed earlier today. Previously, this shutdown was simply slated for some time in early April.
This shutdown will include online co-operative play, internet rankings, and data distribution
The only exception to this termination of online services (for now) are Pokémon Bank and Poké Transporter. While these won’t be affected immediately by the end of service, Nintendo has said online services “may also end at some point in the future”. For other, non-Nintendo published releases with online features, the company asks users to contact the game’s publisher directly.