I've been examining the entry on the wiki about the All, especially the bit that concerns the Priory diagram with the Elder Dragons. I think that we may have missed something here. Each sphere doesn't represent an Elder Dragon as much as it represents the dominant spirit within that magiosphere. So, for example, Grenth and Zaithan co-exist within one sphere (aether magic). Jormag and Dwayna coexist in another sphere (air magic). Primordus and Balthazar coexist in another sphere (fire magic). Kralkatorrik and Lyssa coexist within the next sphere (time magic). Mordremoth and Melandru coexist within the earth magiosphere. And Bubbles and Abbadon co-existed within the water magiosphere.
This would leave Kormir to go somewhere - perhaps in the central orb, for which we have no information as yet.