Somewhere at Sonic Team is a whole "roadmap of Sonic titles," says head honcho Takashi Iizuka, and the devs "think about which game to release in which year"

Sonic Team head Takashi Iizuka has explained how the studio plans out the releases of Sonic games on a roadmap internally.
YouTube on MSN

The essential PS Plus games for March 2025: Dragon Age, Sonic Colors and TMNT. #videogames

Discover the must-play PS Plus games for March 2025! Dive into the epic fantasy world of Dragon Age, relive the vibrant ...
IGN

Sonic Generations Guide

This Wiki covers the Nintendo 3DS version of Sonic Generations. For information on the PlayStation 3 and Xbox 360 versions of Sonic Generations, head to the Sonic Generations (Console) Wiki Guide.