[Update #2]: Sonic Frontiers has now arrived onto PC and consoles alongside some highly divisive reviews.
[Update]: Sonic Origins is coming this July 2022 with four remastered classics and plenty of bonus content.
In stark contrast to the rest of the series, the recently announced Sonic Frontiers will focus on open-world gameplay and exploration. As is tradition you'll still be doing basic platforming, collecting rings, beating up hordes of enemies and smashing head-first into walls at high speed, just with a lot more freedom in how you tackle things than before.
There is sadly no lengthy gameplay preview available just yet, but you can get a decent idea of what the Sonic team is trying to go for through the original announcement trailer. Have a little peek:
As is always the case with Sonic games, I consider myself cautiously optimistic about the idea. If it all works out well I could definitely see Sonic Frontiers being the next big step for the series as zooming around a massive world does sound like a great deal of fun!
On the other hand, the Sonic series is notoriously inconsistent with the quality of its games, so it's anybody's guess how Sonic Frontiers will actually pan out in the end. Whatever the case may be, I do at least appreciate the Sonic team experimenting with new ideas!
Once we get a better look at the actual gameplay I'll make sure to let you know. Until then, you can read a little bit more about Sonic Frontiers over at the official website.