Sega's recent Sonic the Hedgehog livestream showcased various projects in the works, like a remaster of Sonic Colors called Sonic Colors: Ultimate that will be coming to PC as an Epic Store exclusive on September 7. The stream ended with a 30-second teaser of Sonic running through a forest as various digital effects flew off his feet, leaving a glowing trail that formed a circular pattern seen from above. It's a new game from Sonic Team coming to PC in 2022, and that's all we know about it for sure.
If people who claim to have focus tested an early version of the game (via Resetera) are to be trusted, however, it will be open world with "ubisoft towers" and "set on a gloomy, grassy, uninhabited island dotted with ruins", featuring an "xp system with skill tree" that lets you unlock abilities like "spincycle", which seems to be what Sonic's doing at the end of the teaser.
The leaks also claim that solving puzzles around the open world will reward you with orbs that unlock portals to "cyberspace", which would explain all those digital effects around Sonic's feet, where you play levels like those in the fast-moving Sonic Unleashed to earn Chaos Emeralds. Oh, and apparently "a ghost girl refills your ring count".
I'd be more skeptical about these rumors except that one of them, from July 2020, mentions the game was called Sonic Rangers. That name was found in the metadata of a leaked 4K version of the new teaser, and then was just straight-up listed in an official press release sent out by Sega Europe. That press release highlighted everything from the livestream and called the forthcoming game "the next Sonic flagship" (well, "nächsten Sonic-Flaggschiff", but you can trust my German translating ability on this one).
Eurogamer was told by Sega that the press release was "an older version that was shared incorrectly".