Khadgar and Turalyon talked like it was extremely unlikely and it was only though as a possibility in farout future in their conversation. As Gaz told them that Draenor was dying so in time it would have just died out. Also a thing that alliance didn't know they didn't attack there because they though that his portals would destroy eastern kingdoms.
It wasn't a total war, but to safeguard from a hostile force destroy the ones supporting as it protects forsakens.
He only raided supplies, protected warsongs and planned to free orcs from the camps.
They didn't say anything about it in wc3 or chronicles 3 when they made the peace, as such it was a white peace without terms, like returning the lands