While we know a lot about Sonic Mania, we know little about Sonic Project 2017 outside the released teaser video from July. But information about the project recently released and a major part of this information was the gameplay style.
It will be modeled after Sonic Generations, mixing Classic Sonic (2D Gameplay) and Modern Sonic (3D Gameplay) with unique levels for both. Also part of this bit of information is that a new ‘element’ is being added to the gameplay styles, so maybe we will see new moves for the Sonic’s for example.
Source: Sonic Wind Blue