Ya as Baka pointed out, the death of Jiraya was by far the most tragic death for the majority of the Naruto fanbase.
But as to your question, I honestly don't feel that the war is a good story setting for a character to die. I mean, yes you would certainly expect deaths of main characters in a war, but it is not a good setting to have a big character die. I don't know if I'll be able to get my point across... but I'll keep trying.
The thing is, the deaths of Saru/ Asuma/ Jiraya were some pretty extreme ninja battles. Saru was one on one with Oro and had made the decision to take Oro down with him. That would not have happened in almost any other scenario. Asuma and company were taken back by the two strongest enemies that we had ever seen in the manga. If it had not been for Pain summoning them, everyone, including the reinforcements, would have died. As for Jiraya, well all I can say is that Pain was the perfect shinobi and jiraya taking him down once and for all without anyone previously knowing anything about the man is simply unfathomable.
My point is that all of these battles were essentially first encounters with the opponent. Now that all these shinobi's jutsu's have been revealed, having an edo of them kill an important character is not a good plot device. Yes, there were plenty of other new characters that were summoned as edo's, but the battles have simply been to fast paced for any deaths to occur. What I mean by that is Kishi has always dedicated at least half a chapter to a person's death. He has always put a lot of meaning behind his deaths. To be quite honest, I don't feel that Kishi will have any major characters die in the war because it would be contrary to his writing style.
Again, I hope I'm making sense here, but based on what I consider to be Kishi's writing style, and how fast paced these battles have been, I think having a major death in the war is out of the question. I guess since the longer the war goes on, the less villains are left standing, but I still feel that no matter what, the odds are stacked against us seeing a main character die.