Nintendo of Japan announced today that they will be shutting down the Wi-Fi service for both the DS and Wii on May 20.
The shutdown will not only be for Japan, as it will be effecting units worldwide. At this moment both the Wii Shop Channel and the DSi shop will still be running, meaning games can still be purchased online.
What will no longer be accessible for system owners are things such as "online play, matchmaking and leader boards." This information comes courtesy of a statement by Nintendo that was received by Polygon.
While Nintendo has never been praised for the online play of their games, there are some things fan will miss out on once the shutdown rolls around. Both Mario Kart for the Wii and DS had very popular online features, while the DS Pokemon games offered a simple system of trading and battling with trainers worldwide.
Of course this shutdown does not include the Wii U and 3DS, however games for the Wii and DS that are played on these systems will no longer have online compatibility.