Shinryu. I believe that the new Primal is Shinryu.
The reasoning for this is the dropping of the fact that Omega is going to be involved in 3.5 at some point, if the trailer is to be believed. Another thing to note as well is the source of the aether as well for the Primal, which will be Nidhoggs dragon eyes.
What was Omega created for in the first place? To be able to fight Shinryu. If Omega is to be used to battle/contain the new Primal, it would make so much sense for the Primal to be Shinryu, so by the time of the next raid (Rift of Time/Interdimensional Rift) it will make a great callback to Final Fantasy 5 as well.
Does this seem likely and I'm not reading too deep? What do people think of this and is there any other evidence I might of missed?
P.S. How do I hide this behind spoiler box?
Also, I hope that it's OK to post this here as well.