In the first leak trailer we saw Springtrap for a split second, and I know it's him because of the shape of the pupils on the animatronic eyes, plus what looked to me like Spring Bonnie with glowing eyes. I think it's Spring Bonnie because the movements seemed very fluid and not janky like a robot would seem. Plus, now that we've seen William in the flesh, we can infer that there will be a springlock scene, or at least a reference to what happened to him.
I want to see Afton get springlocked, and the bite of '87. I also find it odd that an abandoned building needs a security guard. And why are the animatronics still there? Maybe it's a front to keep them inside so they don't attack other people?
I'm actually kind of glad they're keeping this film's plot straightforward! The game's backstory has become, so I'm actually extremely happy that this movie's lore has been chopped down to just the first 3 games. (no thanks to Security Breach & the Books)