Will human society ever evolve to the point where killing each other is never an acceptable solution?

No - that' s how world works.We may call ourselves Human , but we' re just another animal species.

It' s in our blood.

You have strange logic Gangsta.
Killing people you don' t like is natural, that' s what all animals do. We humans did it a long time ago too.
But nowadays we have an advanced society and we use our intellects and realize that some things can be solved without resorting to violence. Violence is usually not the best way to solve problems in the long run.
That' s why I don' t punch guys I argue with in the face.
Same thing goes for nations and their actions. If a nation has stupid leadership, bad education system or violent traditions/culture then they will resort to violence. But if a nation is civilized, has good leadership and a modern culture then the nation will most likely try to solve their problems in other ways.
Even though violence is in our blood, our instincts, we have learned to control those instincts most of the time.
It' s too bad some people/nations don' t have the same safe control.