With the realms...some of them are afterlife ones, like Hel, and of course Valhala. BUt there's another one that's essentially purgatory. Then there's the dwarf place, the light elves, and the dark elves. And at least one other, besides the three they already showed.
Assume all you like, but as far as what they said...they claim they'll be showing all the other realms.
Since Asgard, and presumably the afterlife realms, all seem to be non-planet kinda places...Midgard may well be earth and it's solar system...or the galaxy. Dunno. But it almost seems more like a dimensional thing than planetary.