Well, depending on how far back the dimensional fracture occurred time-wise, there shouldn't be too much of a geological difference. That takes millions of years or cataclysmic events (i.e. meteor strikes)... if it was only ~10,000 years ago, there wouldn't be too much of a difference. (Wasn't the first Calamity 10,000 years ago? I don't remember where I heard that or if I just made it up whole cloth...)

A-anyway, I was leaning toward dimensional travel anyway... with all the light stuff and barren wasteland from the trailer, and time was already a critical element of the Alexander story and I didn't see them reusing that again quite so soon. Still, now I have to chomp at the bits for a week before knowing how we get there... and all the other questions can stay up in the air. I'm patient enough to wait for Shadowbringers proper.