This is my bet, based on what he has published since his last book and what I suspect could be in it that hasn't been diagrammed.
Likely to unlikely:
Phoenix (on cover)
Cyclomatus Metalifer (published)
Sleipnir (published)
Sea Turtle (published)
Cerberus (published)
Lion (published)
Little Bird (published)
Angelfish (published)
Lyrebird (published)
Locust (published)
Giraffe (published)
Hermit Crab (maybe, published)
Dragonfly (maybe, published)
Asiatic Elephant (maybe, published)
Spinosaurus (maybe, published)
Butterfly (maybe)
Tree Frog (maybe)
Bear (maybe)
Leafy Sea Dragon (maybe)
Raccoon Dog (maybe)
Wasp (maybe)
Ryu-Zin (not likely)
Even if diagrams were in the works for the Ryu-zin, it seems like it would be in a special edition all its own, so I made it least likely. I'd say the wasp is pretty likely despite not being previously published, simply because it is one of his more famous works, like the Sea Turtle, Ryu-zin, Phoenix, and Ancient Dragon. I included his Bear which isn't even on his website, because nice bear models are far and few between

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