So I just saw one weird oddity in the trailer overall. There seems to be a new gym puzzle resembling Santalune's. Either this is a redesign of Sootopolis' gym or another gym overall.
Also I looked at the Hoenn Map carefully and found more weird oddities.
1. There seems to be an ominous structure in the northern part of the map, near Lilycove. I don't know if its the HQ or what but it seems the cave leading to the HQ in RSE is still there, so I don't know what it is.
2. There seems to be yellow buildings located at where the contest buildings were in RSE. If its a redesign or another Battle Tent style thing, I don't know.
It seems to be this yellow building, in the background, near the "PokeMart".
3. Mauville City seems to have a wall around it.
4. There seems to be a new building southwest of Mt. Pyre. I don't know if its an orange building or a weird rock formation.
5. Ever Grande City still remains what it was in RSE.
6. Pokemarts seem to return.
7. Battle Frontier seems to be absent from the games.
8. There seems to be a structure behind Devon HQ in Rustboro.
9. The Lighthouses seem bigger than they were in RSE.