I've seen artworks for some characters. Z-A seems to be set in the same time period as XY but in a different timeline. Some characters seem to have similar roles but different personalities, or vice versa. Having only seen some artworks, I can only comment on what I've seen. I have no information about the characters other than their designs

>Main characters are Calem and Serena again (or have the same design, like Akari and Rei). They seem to be part of a Team, as they have a logo on their outfits (again, similar to Arceus)
>Sycamore is still the Professor judging by his lab coat, but he has a rocker look and holds his hair in place with a guitar-shaped hair clip
>Lysandre seems to be a member (probably the leader?) of the Team we are part of, as he has the same logo on his jacket (different from Team Flare's logo, but still resembles a flame). His design is quite different: he doesn't have a beard, his hair is tied back, he wears glasses and a more casual outfit
>Emma doesn't seem to be an orphan, as her clothes aren't ruined. Her outfit even looks quite valuable. She has an Espurr plushie instead of a real one. She looks sad in the artwork
>Sina seems to be a college student. Dexio has a uniform with the "Quasar?" logo seen in last year's trailer

That's it