Note: This is a spoiler-free article. Everything you see and read here is in the trailer, or is already public knowledge from official announcements and movies released.
This still also confirms the location as Midway City. That's one of the many fictional cities in the DC universe, like Metropolis and Gotham City. If you are wondering, no major DC hero hails from this Chicago-like midwestern city.
And we also see a shot of June Moon in a cave inhaling something dark (an evil entity?), likely to be before turning into the Enchantress.