Sonic Team head Takashi Iizuka demonstrated multiple levels and modes from Sonic Superstars at the Samsung Gaming Project event at TGS 2023. Iizuka showed two levels, Bridge Island Zone and Pinball Carnival Zone, both in co-op and including bosses from both zones. He also demonstrated the 4-player versus co-op and a special stage.
I'll refrain from going any more in depth on the video. If you want to see it for yourself, check out the footage below. The presentation starts roughly 5 minutes in: