The digital rewards at Club Nintendo are being updated, but only partially. Players can still obtain Mario Tennis on the Wii for the next week, but Electroplankton has been replaced with another DSiWare title called Starship Defense. The game promotes itself as a tower defense game in space, with intuitive touch controls and 30 levels to play. More information can be found at the game’s Club Nintendo page. The game will be available until July 29.
The staggered updates are a little weird to see, but hopefully Nintendo keeps folks updated through 3DS messages and Twitter/Facebook posts and whatnot.