Currently, there appears to be a bit of panic as to whether the losing god (currently projected to be Zamorak) will be killed at the end of the world event. It is indicated that may be the case by some of the text in game, but I do not think it’s likely.
As many have pointed out, killing off a faction this early in the 6th age alone seems crazy, but it’s more than that. I was thinking about it earlier. Sir Owen’s introductory quest is yet to be introduced. That quest was confirmed to feature Saradomin in it. Now, it wouldn’t make sense for Saradomin to leave the battlefield midway during the World Event, and the quest could not feature Saradomin at the battlefield, as he presumably will not stay there after the event. So I must conclude that the quest will take place after the event chronologically.
Now, if Saradomin were dead, how could he possibly feature in the quest, and continue to feature in Owen’s quests? His conflicts with staying loyal to Saradomin were cited as a central feature to Owen’s development, and his absence would throw a huge wrench in that equation. Further, Jagex couldn’t possibly know that Saradomin would win the event; as Mod Raven himself said:
So they could not have predicted the event’s outcome when planning Owen’s story. This all leads me to believe that the losing god will not die- Or at least Saradomin would not if he lost, and I’m making the assumption that they share an equal fate upon suffering defeat. I think that’s a valid assumption, but I suppose it’s arguable.