Sonic is going to be all over the gaming world over the next few months. Sonic Unleashed and Sonic Chronicles have both been announced by SEGA and now yet another Sonic title will be hitting the Wii. An ambiguous description of the game gives an idea of what to expect: "The Blue Blur swings cold steel in his new Wii-exclusive adventure."
Updates:
Signs are pointing to the possibility of this being a fake.
http://www.slashgamer.com/2008/07/19/picture-of-a-nintendo-cover-reveals-a-new-sonic-game-we-call-it-a-fake/