Sonic Mania wasn’t the only new Sonic game revealed at the 25th Anniversary Party. At the end of the stream, Takashi Iizuka revealed the debut trailer for Sonic Team’s next game. Like Sonic Generations, the game will feature both Modern Sonic and Classic Sonic. However, Iizuka stressed that this isn’t a sequel, so it’s not Generations 2.
It also appears that the game will have a dark and serious story line. If so, hopefully it won’t be as bad as the series’ previous attempts at having one of those. The game doesn’t have a name yet aside from a working title, Project Sonic 2017, but they did announce that it’ll be released on PS4, Xbox One, NX (!) and PC during Holiday 2017.