The U.S. Copyright Office listing for Sonic the Hedgehog 2 includes a plot synopsis, potentially revealing how Knuckles will be introduced in the upcoming sequel.
Because it hasn’t been announced by Paramount Pictures, Knuckles’ inclusion in Sonic the Hedgehog 2 isn’t officially confirmed.
After the first movie proved to be a tremendous hit at the box office in early 2020, a Sonic the Hedgehog sequel was quickly ordered at Paramount Pictures.
It seems like the movie Sonic the Hedgehog 2 will similarly introduce Knuckles as a threat to Sonic, but because the character is so popular with fans, it seems more than likely he’ll become a hero by the end.