Since the VoH Update, Nahantu can be traveled, but some part of Estuar is still empty.
This attract my curiosity about some empty area of the eastern part of Sanctuary.
The first in mind is the southern part of Nahantu, this empty peninsula is big and can be possibly be a new area in the future?
The second is the eastern part of Nahantu, the only possible way to reach this place is the broken bridge close of the world boss area (The Cauldron). I hope this place will be visited one day. A Teganze Plateau like going to the sea can be only awesome.
The third is the area between Tree of Whispers and the WB Area of Broken Peaks, i mean, with a lake, the islands on the east coast, why don’t make a mountain area with a view points on the broken peaks?
Something more intriguing now is Caldeum east gate. Can be reached going to the west of Alcarnus. The city was destroyed and remain as battlefield between Hells and Inarius Knights. Can this part of the city hidding something? 
There is something about Umir Plateau at Hawezar => The lost city of Ureh, since VoH, the place as change, it’s not like Season 5. A tent is close of the closed stone gate. This place is really interesting how Ureh is considering a glorious city, showed in D3 Trailer.
Probably, all of this will never show the light one day, it’s all about speculation. Will be interesting if the devs can tease us something about all of this in the future.