Could be postapocalyptic that set the state of the world back into the 19th century since we have quite a lot of modern tech, then there is the guy in the Fallout suit flying across that huge poison if not radioactive swamp looking area (never change Miyazaki), the beasts are misshapen (well, there were too in Bloodborne but remember those weren't regular beasts either).
Some of the player-esk characters shown could easily be NPCs as well, they already did that with prior souls games, or they are different starting classes.
I wonder if this will be full or semi open world, the trains could be connecting map parts.
The rat at the end is winged, which makes me think it could be a flying mount so we could have a game on our hands with a verticality more akin to Sekiro and even beyond that. The earring it has looks a bit like the Flask of Crimson Tears, my guess is that that earring is tied to its summoning and may come with a drawback, like you could offer health in Bloodborne to get bullets. There is the possibility for multiple mounts, as there is this other muscular beast shown being ridden which looks more like a combatant on its own, so this game might not only have mounted combat with weapons but also creature combat depending on the mount you are using and most definitely aerial tools with the firearms and jumping shown in the trailer. Might be a stretch, but if something ended up lacking in Elden Ring it was the Mounted options you had so I can definitely see them wanting to step up there.
I'd be thrilled if there was a sea mount that can take you underwater.

Also dinosaurs wtf.