Hey there, Sonic fans. The recent issue of Famitsu had new information for the upcoming Sonic Forces concerning the third playable character. While it didn't outright say who the character will be, it did confirm that Boom!Sonic will NOT be in the game. t also said that the third character will be someone unexpected.
https://www.youtube.com/watch?v=0pOQIq58dec
Who could this character be? Could this be the return of an older character like Mighty or Honey? Luckily, Sonic Forces will be showcased at E3 this year, so we'll know by then.