As we know, the Sigmascape is coming to Final Fantasy XV with the Royal Edition update. It is also implied that Omega might have been created by the ancient people of Solheim, in order to rebel against the six astrals. At this point it is just speculation, but if its true then it has big consequences for XIV's story.
Omega isn't really a problem, but Midgardsomr is. In Final Fantasy XV he is just a common snake enemy. How could he possibly have come from Eos if that is the case? This makes no sense.
Remember that Omega is one of the few beings that can travel between the games. Gilgamesh is also one of these. Midgardsomr is talked as if he did, but we don't know enough about him to be sure. Also nobody really knows if the Gilgamesh in XV is even the same as other games. Nomura, and his teams haven't been quite clear on that. I think they should, because if they're going to deal with these characters, then they need to make sure they are careful about the way they tread on other games.