So, I haven't been in the Emeral Nightmare yet because I live in the EU and still have to wait a few hours. However, Il'gynoth, one of the bosses in Emerald Nightmare does the whole Old God whisper thingy. He has some interesting lines (courtesy of NeoGAF):
"To find him, drown yourself in a circle of stars.
"The boy-king serves at the master's table. Three lies he will offer you."
"Her heart is a crater, and we have filled it."
"The lord of ravens will turn the key."
"Flesh is his gift. He is your true creator."
So... Thoughts?
If I understand that correctly... it seems like Magni (king of diamonds) is not talking to Azeroth, but instead is talking to either N'zoth or one of his minions. And the five keys I understand are the Pillars of Creation, which actually seem to be the key to N'zoths prison (which would also explain why Azshara is seeking them, since she is an ally of the Old Gods). The last line I would attribute to Jaina. Which also doesn't bode well.
Any other whispers from him?
Edit:
Added the last two.