Hey guys, me again with another theory on what the next expansion is but...
Come on, hear me out.
So, Varian said we will focus on keeping Sylvanas contained and retaking Gilneas, how does this link to The Dark Below?
Remember Yogg's Puzzle box? Remember how it said stuff about the bottom of the ocean? Yeah, my Azshara theory still holds to this, but now we can complete the picture with the following.
Remember it saying;
The silent, sleeping, staring houses in the backwoods always dream. It would be merciful to tear them down.
There is a little lamb lost in dark woods.
Look around. They will all betray you. Flee screaming into the black forest.
The giant rook watches from the dead trees. Nothing breathes beneath his shadow.
Just a bit south of Gilneas City and north of Stormglen Village lies The Blackwald.
"Blackwald" is a combination of the word "black" and the German word "wald", meaning forest - hence, "black forest". Thus, it is likely a reference to the Black Forest (Schwarzwald in German) in southern Germany.
The village of Stormglen might be referred to as the houses in the backwoods.
Now what else is important; The original worgen, the Druids of the Scythe, lived in the Blackwald.
In the center of the Blackwald is a big tree called Tal'Doren, which is identical to the tree Daral'nir where the Druids locked away the Druids of the Pack, which were the first Worgen, in The Emerald Dream.
Druids of the Pack/Scythe Lore Bit
The Druids of the Pack were druids who turned towards Goldrinn and shapeshifted into Pack Form, which originally were wolves. They were mindless and savage in that form, attacking Night Elves and demons alike, so Pack Form was forbidden by Malfurion, making for some very pissed Pack Druids. Eventually, the Scythe of Elune was created, hoping it would temper the mindless rage of the Pack Form Druids, but it also made Pack Form a humanoid form, creating the first Worgen. Their bite also became infectuous (for some reason), and eventually the Scythe was used to seal them away under Daral'Nir.
So, the next expansion will feature The Blackwald, Maybe corrupted Worgen, Naga's, Emerald Dream and such.
The Blackwald holds strong connections to The Emerald Dream, and is a black forest with lots of dead trees.
EDIT: We also know Tirisfall Glades is around the corner, and we know there's something buried below it.
Blackwald and Tirisfall might be in connection to eachother underground or in the Emerald Dream or something.
Here's a picture of the Blackwald for anyone not convinced this is a very black forest with dead trees.