This feels like a huge middle finger to the Sonic voice cast on Sega's part.
I mean they've done it before, they like to change the voice cast pretty often, depending on the character. Sonic went through 2 other actors before RCS, Knuckles and Tails went through 6 already I believe. But, the current voice cast has largely been on Sonic for 10 years now (though Tails and Knuckles got replaced more recently), with Mike Pollack as Eggman/Robotnik for 17 years I believe, so alot of people thought that Sega had a voice cast they were happy with and were going to stick with even longer. But it seems that is not the case.
I assume they are either planning to use the Sonic movie voice cast for the next game and release the next main game as a tie-in for Sonic movie 2 in April 2022, or that they just wanted to refresh the entire game voice cast ahead of the upcoming new 2022 Sonic tv show for Netflix, Sonic Prime, and use that new voice cast on the show.