Sega and Marvelous Entertainment have both released teaser sites featuring a countdown timer. Both of the timers end on the same day.
Marvelous Site: http://www.mmv.co.jp/special/game/30/
Sega Site: http://pole.sega.jp/
A lot of you may be thinking that it is Zelda because of the Triforce, but I don't think it is. I think it's an F-Zero game. The mushroom on the Sega site is an emblem that can be placed on the F-Zero vehicles. Triforce was also the name given to the team that made F-Zero GX, which was made up of Sega, Nintendo, and Namco.
lol
f zero + zelda = a epic fail game
"Can't live with the guilt? fine...die with it"