The game is separate from the previously announced Sonic Boom.
Earlier in the year, Sega announced Sonic Boom, a new Sonic title that takes some... artistic liberties from what fans have expected from the series. Sonic Boom is being developed by Big Red Button though, and not the core Sonic team that brought us Sonic: Lost World last year. Team Sonic's Takashi Iizuka has now told Japanese outlet 4gamer that his team is, in fact, working on its own new game, completely separate from Sonic Boom.
"At the moment, the core Sonic team at Sega is working on a new title that will use the traditional look and mechanics of the series, which will get more details later during the year," said Iizuka, which i'm sure Sonic fans will be glad to hear.
As for Sonic Boom, he explained that, "At the same time, Big Red Button, an entirely new studio, is working on a new version of the entire game universe, called Sonic Boom," adding that it "is designed to accompany the delivery of a new range of toys and a new cartoon series."
So in short, he has basically told us, "Don't worry about Sonic Boom, that's just there to sell toys and cartoons. You'll get a proper Sonic game later."
Sonic Boom will release on the Wii U and 3DS in 2014, and last we heard, a "Next-gen" Sonic title was rumored to be scheduled for 2015, which might just be the new title Team Sonic is working on.
Sonic: Lost World recently got some rather cool, completely free Zelda DLC.