I don’t know what Sylvanas’ real plan is, if she even has one. But people do tend to overlook that Sylvanas’ original plan was to split the Alliance by taking Teldrassil and expecting Genn Greymane to leave to Alliance for prioritizing taking Teldrassil back over Gilneas.
Instead people tend to focus on Saurfang sparing Malfurion and Sylvanas burning Teldrassil as a response. But there Sylvanas throws the baby out with the bathwater, not necessarily because she actually thinks it through, but because she’s in the middle of an emotional break down.
The following is my analysis of Sylvanas’ internal monologue from A Good War leading up to the “Warbringers: Sylvanas” animatic:
To start, the following sure sounds like genocide, doesn’t it? But seriously, this is just Sylvanas moving the goal post. The plan was never to end the Night Elves as a people, and it was never about the Night Elves losing their leaders, yet here we are with Sylvanas going on about it:
This battle was not about a piece of land. Even Saurfang knew that. Taking the World Tree was a way to inflict a wound that could never heal. Losing their homes and their leaders would have ended the kaldorei as a nation, if not a people.
This next part is just emotional rambling, as the only way this would have bled the Alliance would have been if Genn left it, leaving Sylvanas with just jumping to conclusions without any reason to believe any of this:
Even the loss of one leader would have been enough to create a tide of despair. The wounds of this battle would have bled, festered, decayed, and rotted the Alliance from the inside out.
The next part is how Sylvanas expects the attack on Undercity and/or the attempt to retake Teldrassil would go:
Anduin Wrynn would have lashed out in a final, desperate war, looking for a miracle, because only a miracle would save them.
And then her thoughts devolve into something not related to how Anduin would behave after Teldrassil was taken, but setting up her own self-chastisement:
But a miracle already had. A miracle granted by the honorable hand of a foolish old orc.
And an overconfident warchief. Best to lay blame where it belonged. This was her mistake as much as Saurfang’s.
And then Sylvanas’ thoughts start to spiral out of control as she starts to panic that she had allowed things to possibly get beyond her:
This conquest of Darnassus would rattle the kaldorei people. They would grieve for their lost, fear for their imprisoned, and tremble at the thought of the Horde ransacking their homes. But they would not fall to despair. Not anymore. Malfurion’s impossible survival would give them hope. Their wound would heal.
Even in this dark hour, they would say, Elune still watches over us.
At this point Sylvanas just starts rambling incoherently and emotionally, like someone having conspiratory thoughts that the world itself was out to get her:
And that was almost certainly true, wasn’t it? Elune had intervened. Perhaps she had even stayed Saurfang’s killing blow. And she wouldn’t be the only force beyond the Alliance to oppose Sylvanas’s true objective.
Sylvanas’s anger grew cold.
She had known this would happen. It had simply come sooner than expected. That was all.
And even through all this, Sylvanas still was going forward with the plan to take Teldrassil:
She strode toward the shoreline, ignoring the last few skirmishes and the wailing of those unfortunate kaldorei who had been unable to escape Darkshore. She studied the shape of Teldrassil towering above her in the moonslight. Soon, it would be in the hands of the Horde.
“Secure the beach,” Sylvanas said. “Prepare to invade the tree.”
And at this point Sylvanas didn’t even seem to know what her plan even was any more and was in a mental spiral ready to be pushed over the edge by Delaryn:
A wound that cannot heal. Sylvanas needed to think of a new way to inflict one. There was no turning back.