Being echo the power to break boundaries of existence ( i've said that alot lately! damn it !) well, sayng it again. Being Ysayle a very powerful echo user, i would not be surprised if she comes back/ preserves her aether and mind in the aetherflow. I really hope that she comes back, but with this sultana thing. i have little hope, since...

Nael is dead.... LOLNO- LOLYES!
Louisoux is dead ... LOLKINDA!
Sultana is dead.... LOLNO!
Scions are all dead! LOLNO!

it wouldn't make a bit of sense if Haurchefant comes back, I can see Ysayle coming back to be honest but....