Info released today-ish :
IGN Expansion info
Also, an image link for some of the items coming with the expansion.... (Sorry, doesn't really show any details, just names and icons)
Expansion Items
Annnnd a short interview between PS and Bungie regarding the x-pac:
PS Blog: The Dark Below
The Dark Below - Expansion Details
Re: The Dark Below - Expansion Details
Good thing we are all on ps4, Xbox isn't getting a second strike now.