Aside from the ones we have access to, Hoenn and Sinnoh are nearby but... inaccessible. I believe Sinnoh is across a fairly impassable mountain range, and I believe Hoenn's to the south.

Unova, by contrast, is rather far away, and Kalos is... well, I don't even know. It seems to have come out of nowhere, really... the locals have hosted a gala in April at a secret location the past two years, and we were lucky enough to encounter some guests hailing from there.