Surprisingly, Sonic Team isn’t making Sonic the Hedgehog 4. Dragon Ball Z: Budokai and Street Fighter IV developer Dimps is.
Dimps worked with Sonic before. The studio developed Sonic Rush and Sonic Rush Adventure for the Nintendo DS. Both of those were 2D Sonic games and stuck to Sonic series traditions too.
Giving Sonic the Hedgehog 4 to Dimps was probably a good idea. Fans longing for a traditional Sonic game have been mostly disappointed with Sonic Team’s werehog and knight transformations. This also leaves Sonic Team free to work on non-Sonic projects like Phantasy Star Zero.