*Credit to Tauror for the Information. Keep in mind the content below is NYI (Not yet Implemented)
Lord Godfery an NPC from the Worgen Starting quest who commit suicide rather than serve a Worgen King is risen as a Forsaken. He leads the attack on Pyrewood and Sacks it Sylvanas shows up to gloat about her victory then Godfery makes his move and shoots her in the back of the head.
SHE GOT BETRAYED AGAIN! The Val'kyr who come to her aid supposedly rez her at a later occasion?.
Here is an image of Godfrey. After he slays Sylvanas he kidnaps Crowley's daughter and uses her to call a ceasefire between the Gilneans and the Forsaken.
He makes his way to SFK where he will presumably be the final boss in patch 4.1
I will probably add more as I investigate this further.
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The 7th Legion shortly thereafter or before, moves in via submarine and occupies Gilneas. Effectively putting it under Alliance control.