Even if it doesn't look like it, Central City IS a part of the wider city setting in Shadow the Hedgehog: But that makes me wonder if the Black Arms' original attack that supposedly destroyed Westopolis (but don't worry everyone was evacuated so nobody died) covers the whole collective city or just the Westopolis part. Not that it seems to matter to the rest of the world. Seems like people take this litterally as making it a part of the black arms rather than something that the Black Arms knew about etc. Exploring Space with Sonic seems like a fairly obvious thing that they haven't really done in a (canon) game but have done anywhere else. I think the next logical step after frontiers really is just looking to other planets/planetoids with different species and settings. (I'm not counting Colors because outside of some light theming it's still more like the Death Egg with somewhat more natural environments attached and only one race of aliens.) One thing I would love them to work up to if anything was possible would be a canon version of Chronicles to see some of those races again.