Sonic Armageddon

Sonic Armageddon was a planned film by Ben Hurst (writer of Sonic: The Animated Series and Sonic Underground) alongside Ken Penders, the writer of Sonic Archie comics) Based on the Saturday morning cartoon Sonic: The Animated Series, and proposed to DreamWorks Pictures.

Plot
From the looks of the storyboards, it looks like the film would be about Mobius exploiting, so it would likely serve as a sequel to the Sonic the Hedgehog animated series.

Why It Was Cancelled

 * 1) DreamWorks expressed no interest in the film.
 * 2) Sega was already busy with Sonic X.

Result

 * The film was permanently cancelled.
 * Sony Pictures took over the rights to make a film, but was later sold to Paramount Pictures which released the film on February 14, 2020.