I'm wondering whether Urianger is actually correct. In the end, we don't have a scooby about how these "hearts" function, and the only plot-relevant thing that comes to mind is the Heart of Sabik. The funny thing is, looking at the
Wikipedia page on it, there is this little interesting tidbit, relevant part highlighted:
It bore the traditional name Sabik, from the Arabic السابق al-sābiq
"the preceding one", of uncertain reference.
They said they were going to pick up on the Heart of Sabik in a future plot, and it looks like an obvious way to resolve that loose end.
Still, with Zodiark "dormant" and divided, it's not a foregone conclusion that the Heart would be, too. Venat apparently would not fade from the world by becoming Hydaelyn, and this "Elidibus" we're seeing thus could be the original. The wrinkle with that is that he does refer to Zodiark's will as that of a third person, e.g. when speaking to Lahabrea, but that can be explained away by saying that once he is in that form, it is effectively another entity altogether, like all the other Primal with a vessel transformations we've seen. It'd be consistent with Elidibus's affinity to Zodiark.
Another layer to this is that, if the original was somehow destroyed through the Sundering, perhaps it would fall to this "Elidibus" to sacrifice himself too, to become the revived Zodiark... and that is where Zenos and "Asahi" may fit into it. If Elidibus - original or otherwise - should perish or otherwise forego his agenda, this third party may be baiting Zenos into becoming the Heart of Zodiark, with the goal of both him and Hydaelyn being destroyed. I certainly think it could be a fragment of the 14th, who spent some time with the Ascians.
Either way, I hope they write him well and avoid having him killed off for silly reasons/in stupid ways.