Okay, so we know what Poseidon is. It's a mermaid that can talk to Sea Kings, and it's Shirahoshi.
Now, Uranus (sigh) and Pluton haven't been confirmed.
What you think they are?
My ideas are:
-Pluton is supposed to be a ship that is very destructive. I think it's either the Noah or the Sunny once Franky fully upgrades it.
-Uranus is the sky god or whatever so it might like a plane or spaceship. I think if Franky meets Vegapunk, they might create it together.