An altar of him resides in the Dunwich Building in Fallout 3, think we'll hear more of this Lovecraftian-style horror in Fallout 4?

http://fallout.wikia.com/wiki/Ug-Qualtoth

It's possible, some have speculated that there could be a Salem DLC and I wouldn't mind seeing a little more of Ug-Qualtoth and a bit of implied supernatural stuff.

There was a ghost quest-giver in Fallout 2, Anna Winslow. But she's way in the West Coast.

I would like this. Would be nice if we got a little fishing village with some rather strange inhabitants and a side that uncovers their dark secrets. Oh crap, I just described a quest from Oblivion. Well if they could do it differently I would certainly love a Lovecraft inspired side quest or location.