Took this from the new map and instantly was pulled to where Black City/White Forest was supposed to be. Now there is a Mountain that is frozen over. Added to Chargestone and Mistralon Cave's freeze over this is the second major freezing that I noticed.
Grey mountain, hmmmm. Nah I think name-wise they'll go pretty creative, but as for its purpose, idk, it kinda lacks city elements from the looks of it, so it can't be a Black City/White Forest merger type deal. :(
I hate to be the one to tell you this but the grey mountain has always been there and White Forest/Black City is slightly south of it. What you zoomed in on isn't Nimbasa City, it's the Entralink. The airport is totally new though and so are the two islands Kaori pointed out.
It does happen to be slightly above where Black City/White Forest was and the actual area (though a bit to thick for me to see through) I can only make out the tree skirt that is near the symbol for the City/Forest placement and the rest is fairly blank.
Guess we'll have to see a clearer map to make the whole thing out.
Maybe this mountain is the place you get Kyurem at? Idk, just a wild guess. Like Wings said, it was there before, but with them adding a major freeze-over on it, it makes it a little more suspicious. So I'm guessing, and hoping, it has something to do with the main plotline.
"Oh, fantastic! What did you think? My team was pretty cool, right? It's a bit embarrassing to show off, but I love to show their best sides!"