Mario and Sonic at the Rio 2016 Olympic Games is launching on March 18th for 3DS in North America and April 8th in Europe. The Wii U version is also dated for June 24th in North America. No release date has been announced for the PAL Wii U version of this title. Rugby Sevens has also been announced as a new mode in the game as well.
More details to follow.
Source: Nintendo Direct