Long horns like these? I would go with distant past. There a number of things that seem more primal than what we see in BotW. TotK may start out right after BotW ends, but that doesn't mean it has to stay there. It's pretty clear we've only been given a tiny glimpse of a very narrow part of it.
7 tears and 7 ridges on the dragon's back (or whatever they end up being) - though there are 10 in the green logo background. So probably nothing.
This is the only other living thing present in the trailer. I'm going to guess that the black and white portion of the game is only a smaller part of it and not a whole part of the world, sort of like the Silent Realms in SS. (though Link also gets a similar power to rewind objects, like we've seen, just on a smaller scale) Perhaps you need to gather remnants and rebuild the skylands (as has been suggested already) and you need do this each time to clear up a new sky region and make it accessible (in the past and/or the present). Maybe his new toolbelt thing is the power source that enables this skill and requires levelling up. Who knows.