After the reception to the sometimes overly dark (torture?) Sonic Forces, I hope Sonic Team is ready to course correct. But we won't truly know until 2021, which is when the developer says Sonic is making his next big splash.
Speaking to Game Informer at E3, Sonic Team boss Takashi Iizuka explained again that 2021 is "the next big year for Sonic," and that they are "preparing" for it already. Although stopping short of outright confirming a game release, we do know that the studio is creating a new mainline Sonic game, and 2021 just so happens to be the 30th anniversary of the franchise. So! He probably did just confirm it.
Of course, just like Maniabalanced out Forces, I really hope we get another retro follow up just in case. Although mainline Sonicgames are very hit and miss, fans always hold out hope that the next one will actually bring the subseries back to its Adventure glory days. And hey, it has happened, so technically it could happen in 2021!
What's happening in 2019? Hopefully the thing I embedded below. It should be a great time.
Sonic Team Says 2021 Is The "Next Big Year" For Sonic [Game Informer]