So i was thinking how stupid it is if Sylvanas actually burns down Teldrassil, And how it do not really fit that Saurfang is seen in that picture next to her.
What if it is actually Thalyssra that burns it down? She steals a shard from the sword of Sargeras, And as she tells the player on the end of the sunwell enocounter, "As for me, I am going to test my skill in Ashenvale. For the Horde!"
She might be the dying Night Elf that is shot the in the back, Sylvanas finds out but arrives to late to prevent an all out faction war.
The picture does not fit her 100% but that might have been done by blizzard deliberately as to not spoil anything.
I dont know, I might just be fishing for answers that are not there.