I'm not as negative as most when it comes to modern Sonic games, but Frontiers has me concerned.
First off, open world, I'm not a fan of that. Sega have obviously got it in their head that empty looking open worlds is what everybody wants right now. They did the same with Phantasy Star, and it's been a mess for nearly a year because they don't seem to know how to make an open world game. It also feels like they are jumping on this open world bandwagon too late. It just feels like they want their own Genshin with Phantasy Star and Zelda: Breath of the Wild with Sonic.
Secondly, they seem very reluctant to actually show anything. Even in that teaser, there wasn't much to be seen.......and this game is supposed to release at the end of the year? That is a major red flag for me.