How would that stop the war?Jaina will probably kill Thrall. have a break down realising what she has done. and the Horde with Martyr fueld momentum raises Kul'Tiras to the ground snuffing out the Proudmoore blood line.
Nathanos dies to Genn and Sylvanas losing the only person she cares about left in the world puts the rabid beast out of his misery.
This will be how the 5th War ends.
Thrall Cairne and Vol'jin look on at their Horde that despite all odds has survived and endured.