Tyson Hesse will not participate in the series from Netflix, which he announced himself. He also added that there will be no Classic Sonic in the series due to SEGA's intentions to stick with Modern Sonic.
"The Illuminerdi" shared some information about the sequel. There was both old and new: - Knuckles got a much bigger role in the film than a cameo. He will keep his skills and stay true to his incarnation in video games. The voice actor for it has not yet been found. - A new character named Randall will appear in the film. It will only interact with people. - The search for a famous actor for a cameo is underway. Samuel Leroy Jackson and Chris Rock were mentioned. Here is the source.
Tyson Hesse (Designer of Sonic in film) and Fill Marc (Storyboard artist who participated in "Rick & Morty" and "Duck Tales") will work on the sequel. That was reported by Fill himself, but he later deleted his tweet.
Some new information from documents of Paramount Pictures: - Codename - "Emerald Hill" - Filming is planning to take place in British Columbia, starting from 15 march to 10 may 2021. - The documents do not provide information about management positions and actors.