Season 3 - The Lost Season

Sadly, there was never a season three made. Sonic SatAM had
it's plug pulled before one was made, even with the setup for
the next series at the end of episode 26. Thanks to a fan,
At least a breif summary of what was meant to happen was
given:

Though the series ended with Season 2, there were more episodes planned.
According to writer Ben Hurst, quoted on Sonic HQ and Fans United for
SatAm), the third season would have featured Snively briefly attempting to
take over, but he quickly fails; he would then accidentally release Ixis
Naugus from the Void, who would take over as the main villain with Robotnik
as his lackey. (Naugus is also the person whose eyes were seen behind
Snively at the end of Season 2.) King Acorn would also be freed from the
Void and Snively, reduced to nothing, would later defect to the Freedom
Fighters (which briefly occurred in the Sonic Archie comic).