Everlasting
Everything stays.
So since there's only six stadiums clearly visible on the map.....
...what if there's only 5 Gyms + Elite4/Champion? I know people like to think that the Victorian and Medieval looking cities, but the bits that maaaaaaaaaaybe, perhaaaaaps, poooooosibly could be gyms don't feature any of the elements the other stadiums have (no logo, no "spikes", no room for spectators...)
The official website has already confirmed that there are thankfully 8 gym badges to collect in the Galar Region:
"The Gym Challenge is a true celebration of Pokémon battling! Participating Trainers strive to collect all eight Gym Badges, and only Pokémon Trainers who have been endorsed by specific people, such as Gym Leaders, can join in."
edit: Greninja'd. In any case I wonder if that means two gyms have different infrastructure or if the map really is that unfaithful to the actual region.