Every time before the next xpac, people think Emerald dream is always next. I had a argument with someone that thought emerald dream was next xpac 1 week before mop was announced. I thought it was mop because I read a 50 page forum of wowchampion talking about this disc called "Mists of Pandaria" and it seemed to be something to do with pandarens.
Before wrath, people thought Emerald dream was next, same happened before
This is why
once upon a time some data miners discovered unfinished Emerald dream territories I believe either during or slightly before BC. There were three partially constructed territories that used textures and such that have never had the pleasure of gracing Warcraft (Accept for a Jade humanoid statue which was placed at the center of emerald dragon shire).
It was basically a field with odd flowers models, an emerald forest of floating twisty rooted trees and some zone with no textures but jade statues. It also featured some interesting ground structure samples that took the form of swirly symbols, they were like dirt mount art.
Several of these videos come up whenever someone searches Next WoW expansion on youtube, which results in thousands of people seeing these videos and thinking they are spoilers for the next expansion without looking at upload dates. This has been happening for years. People don't realize that it is an incredibly ancient datamine with polygon counts far too old for our current model, in fact it was obvious they were made during BC production because some of the Textures were recognizable from the era.
It's also because little is known about the emerald dream and it keeps getting mentioned in warcraft lore, more so than the elemental planes or the twisting nether (heck most lore noobs recall their first experience with it as druids or in Wailing Caverns). So to the average lore clueless WoW player the emerald dream is this big over hyped mystery they really want to see and think every expansion should be it.
Truth is despite blizzards intentions on making it they have since crapped it with knaaks terrible book known as stormrage, Perhaps one day they'll make a territory out of it or perhaps an instance but they have no intentions of making it available as an expansion.