Now there are lots of people that rumoured that either “Mario and Sonic 3” (it's codename) was a party game or a sport game. As SEGA and Nintendo said that it is now Mario and Sonic at the London 2012 Olympic Games ( マリオ2012年ロンドンソニックAT北京オリンピック [probably like that in Japanese]) and it will include new sports such as horse racing and football (soccer). This game could possibly be the last Sonic game or either Sonic Generations.
I once published a Sonic Show video of the game, when TSS (The Sonic Stadium) thought that it was called “Mario and Sonic at the Cockney Olympic Games” just before the title's announcement.
The Nintendo 3DS version will have 50 sports included, unlike in the Nintendo DS version of Mario and Sonic at the Olympic Games (known in Japan as Mario and Sonic at the Beijing Olympics). Sorry, but they'll be no Nintendo DS version of the game and Sonic Generations will possibly be the Nintendo DS Sonic game!