Zaros wasn't exactly involved in OSRS Items the primary God Wars Dungeon; the main God Wars (that ended with Zamorak burning Forinthry and establishing the Wilderness) began following Zaros lost his body. The battle for the Godsword started, the army were able to sneak into the temple, where Nex was trapped and they led to Nex to escape her trap.
She started destroying everything around her, and the 4 factions joined together to entrap her with the Frozen Key. This time, everyone got a quarter. I hope that the next God Wars dungeon isn't like the one in 07 scape, which is the same concept, but in the wilderness.
I was not talking about the first God Wars Dungeon but the actual second Gielinorian (or just the principal God Wars) God Wars in which Zaros was a part of the battle in spite of Zaros' absence because of losing the majority of his power and no body, as you stated. I was trying to answer "What other gods were involved? (in the primary God Wars)" Sobend's question.
They don't necessarily have to make a God Wars dungeon that's about past God Wars. Maybe they just want to make a dungeon to support the current God Wars. It could be a part of the Tuska world event.
From what I gathered from it it seems to me that it will be the most important world event to date and could even last longer than the two previous events. They even mention "there's going to Buy RuneScape Gold be some massive, long lasting ramifications to the world" which could very well mean they will change parts of the landscape and add new battlegrounds/dungeons.