It was announced in the latest Nintendo Direct that the next installment in the Sonic The Hedgehog series is Sonic: The Lost World and it will be released exclusively for the Wii U and 3DS.

Not much is known about the title yet, just that it is another Sonic platformer, possibly along the lines of the two latest main-series games Sonic Colours and the 360/PS3 versions of Sonic Generations. 

Satoru Iwata confirmed that Nintendo had entered into an exclusive partnership with SEGA to bring the new Sonic title exclusively to Wii U and 3DS.