Sonic Frontiers 2 or another Sonic game with the Frontiers formula.
The first game was really good and promising. Technical problems aside, the experiment the Sonic Team did (the open zones) worked great and was the best part of the game. After the success of Shadow Generations, which also implemented the Frontiers formula on an smaller scale, I’m pretty sure the next big game would be way past Amazing.
It is both! A rerelease and a new game put together. The Shadow part wasn’t just “new content”, it was a whole independent story with new game mechanics and such. It was weird but it worked out pretty well.
I have the idea that it was a way for the Sonic Team to test again the Frontiers formula without remaking all Frontiers the ground up. They were like: “Does the people really REALLY liked this formula?”, and after the success they’ll be like"Yep, they like it. Let’s go for it".