I think Sega's raring to announce a sequel to Sonic Colors which is probably the freshest Sonic 2D game that was good in every way.
I saw AmiAmi selling this Sonic Colors anniversary pack for Switch and PS4.
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Then I log onto YT and see IGN waving a new limited series Sonic Colors show:
https://www.youtube.com/watch?v=3TI6s6Wp5p0
With Sonic's "birthday" less than a month from now, my guess is that they're going to announce Sonic Colors 2.