The news comes as a surprise considering Nintendo's Wii was in production until October 2013.
As of May 20th, 2014, the Nintendo Wi-Fi Connection service will be discontinued and it will no longer be possible to use online features of Nintendo DS/DSi and Wii software such as online play, matchmaking and leaderboards.
The following services are not affected by the termination, and will continue to be available after May 20th:
Internet Channel Nintendo DS Browser Nintendo DSi Browser Nintendo DSi Shop Nintendo Wi-Fi Connection Pay & Play Wii Shop Channel YouTube
Wii U and Nintendo 3DS games will not be affected but it will not be possible to use online features of Wii software played in Wii Mode on Wii U, and of Nintendo DS games played on Nintendo 3DS family systems.