The partnership that should never have happened, but did, will return together again for the 2012 Summer Olympics that is set in London.
This will be the first Sonic and Mario game to debut on the 3DS and Sega has a good eight months to get this game right. Mario & Sonic will have around 50 or so events and offer both online and offline play.
There is no official date for this game but it’s safe to say that it will launch around the time of the 2012 Olympic games. We should know more around June when E3 takes place on a solid release date.