Nintendo has announced that a lot of features on the Nintendo Wi-Fi Connection service for the Wii, Nintendo DS, and Nintendo DSi systems will be unavailable after the 20th of May, 2014.
This means player will be unable to access online features like online play, matchmaking and leaderboards. This includes all online features of Gen IV and Gen V Pokémon games, as well as the Mystery Dungeon and Ranger games.
Other online functionality, such as access to the Wii Shop Channel, the Nintendo DSi Shop and video-on-demand services is unaffected until further notice.
For a full list of affected titles, you can check Nintendo’s official announcement.