I might have an upcoming chance to finally visit Shedd which I'm really looking forward to, and found what I believe is the most up to date
walkthrough tour that shows the entire aquarium, if anyone else was interested.
I don't mean to make this a fantasy post but I really overlooked the species they already have, I wouldn't be surprised if they don't get a ton of new species in terms of the Whalefall exhibits. I definitely they think they could fit a 3rd tank in this area, especially since they already confirmed the Pacific Hagfish which don't need much space at all since they stay in the same spot 95% of the time.
Honestly, what I could see the plan being is:
Tank 1: Pacific Hagfish (confirmed new species)
Tank 2: Japanese Spider Crabs, Japanese Armorheads, Snipefish, Boarfish, Redfish (all moving over from the "Oceans" gallery since they'll need a new place to go anyways)
Tank 3: Giant Isopods (I don't see why they wouldn't bring these in) though in the concept art, this tank does show it having fish in it so I could also see the Snipefish or Boarfish moving here as well instead of the largest tank with the Spider Crabs.
I don't see where the Cherry Anthias could go in the new space unfortunately since the temperatures would be too cold for them, so hopefully they're moved somewhere in the Wild Reef instead of being phased out.
I imagine most of their focus for the new gallery is going to be on the Caribbean Tunnel since they already have a good roster of species for the Kelp Forest Tank and the Whalefall exhibits. Only 1 year left till the gallery opens is really exciting, hopefully we'll get some new updates in the coming months.