I actually think they could go the Pandora's Box scenario.
Sha of Hope. Although not innately evil - which is why the emperor never encountered it, it is evil when combined with the thoughts of man. Such as the Alliance having hope they can destroy the Horde, etc.
Either that or Pride.
Sha of Procrastination - He'll show up sooner or later. Probably later.
Only known thing is that the seventh sha will come from the PC or something else.. We also know it is below pandaria, somewhere. And that it hasn't been unleashed... Perhaps the 7th head didn't breathe. Perhaps it has nothing to do with Garrosh, and Garrosh just comes in and steal the thing that makes the sha reappear or whatever sha artifact lies in that place, I could see it tie in with 5.3 ending the Pandaren campaign.
I think they are going to go a completely differnt direction with the 7th Sha. I think the 7th Sha will be the Sha of Life. (or Curse of Flesh)
Sha of MADNESS
You see, there's this thing called "aggro". It's a very complicated, very technical roleplaying expression.
Loosely translated, it means "the priest dies".
My understanding is that the sha of violence embodies a desire for violence, the desire to do violent things. One could also call it the sha of bloodlust for example, though I'm still not sure if that counts as an emotion.
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Sha of Pride (or your 5th option).
PEPE SILVA, PEPE SILVA
Sha of Guilt.
What ability did the very first Sha you fight on Pandaria use against you? Overwhelming Guilt.
Where did the massive Sha that you first see on Pandaria go?
Those are the two reasons why I think the Seventh Sha is the Sha of Guilt. The Sha of Guilt also ties into Garrosh's story better than any of the other ones:
What was Garrosh's defining emotion before meeting Thrall? Guilt for what his father was supposed to have done.
Why is Garrosh so determined to make things better for the Orcs? Because they are suffering for what his father did.