Take a look at this gameplay using Sonic Forces third playable character in the Updated Chemical Plant and Casino Forest Zones! (gamespot.com)
A few weeks ago, in an interview with Famitsu magazine, Takashi Iizuka explained that the third playable character in Sonic Forces was an «unexpected character», that plays an important role in the story, and «embodies the overall features of the game». (perfectly-nintendo.com)
It's at this show that SEGA plans to reveal the third playable character. (perfectly-nintendo.com)