Takashi Iizuka, an executive with the Sonic team, provided information about the game at an event in Tokyo. We will learn more at the Sonic 25th Anniversary fan event on July 22, which is taking place in San Diego.
We at Sonic Team are developing a completely new game. The most important thing is not the fact that the series survived for 25 years, but how many games [were] developed. Our goal [is to] add something new and overcome any potential hardships.- Iizuka
This entry in the series, called Sonic Boom: Fire & Ice, will be released for the Nintendo 3DS on September 27. Before it was delayed, the game was supposed to arrive in 2015.