**VERY MINOR SPOILERS** Isla Sorna in JW: Fallen Kingdom?

there are no dinos on sorna, but they could make a new population on the other five deaths though.

I'm days late but I still wanted to explain it anyway so yeah, Ok so apparently illegally bred Dinosaurs(Spino, Cera, Anky, and other species that I couldn't remember) somehow screwed up Sorna's ecosystem which resulted in dinosaurs dying out. So Ingen rescued the ones that survived and moved them to Isla Nublar for future attractions( I like to interpret that they were put in the restricted area which explains why we didn't see the new dinosaurs like Carno, Allo, etc in JW).

Yeah, the JP Wikia says that Spinosaurus, Ankylosaurus, Ceratosaurus, and Corythosaurus caused a large drop in dinosaur populations. The survivors were transferred to Nublar, implying that this drop happened before the Nublar incident of '15.

So the answer to the OP's question is needless retconning then?

Wasn't it explained in Lost World: Jurassic Park (both film and novel) that Isla Sorna was where InGen created the dinosaurs before moving them to the park resort on Isla Nublar, and wasn't it shown in said movie/novel that Sorna was declared a natural preserve for the Dinosaurs.

Considering the small number of Dinosaurs that survive in the new movie (seen in trailer, thus not a spoiler) is retconning Sorna out of functionality really a good idea?

Keep in mind that I haven't seen the movie yet, so I have no idea if they mention Sorna as a safe place to relocate the dinosaurs.

I'm sure the eruption is so powerful that it would make the 5 Deaths inadequate for the dinosaurs.  

The eruption seen in the trailers occurs on Isla Nublar, effectively wiping most of the Dinosaurs on the island except for the 11 species they manage to rescue.

This along with the needless retconning that Isla Sorna's Dinosaurs all died out, now means that any Dinosaurs that survive Fallen Kingdom are the only Dinosaurs left alive, which doesn't exactly bode well for the future and expansion of the franchise; that and the writers need to create a super-Dinosaur for each instalment - will JW3 have an Indo-Spinosaur? 

@Gavin, Trevorrow stated that the Indoraptor will be the last hybrid featured in the franchise.  No hybrids for JW3.

Perhaps they didn’t move Nublar’s dinosaurs because Sorna could potentially erupt if Nublar did? Or they’re saving Sorna for JW3?

Sorna is also volcanic in both the films and books. Ludlow said in TLW "Hammond ran everything on Geothermal Power". 

Mills mentions Sorna by name and Lockwood mentions what Hammond said at the end of TLW.

I recommend going on the Dinosaur Protection Group website and Klayton Fioriti's YouTube channel for JP lore information. 

Well if I remember correctly from Lost world they mention Isla Sorna to also have volcanic activity. Even with there being no more dinosaurs there to attack the ones from Isla Nublar what would be the point of moving them from one volcanic island to another.

Well since the spinosaurus is technically Wu's first hybrid, its quite possible that the spinosaurus alone was able to cause the instability on Isla Sorna. Also its not a retcon Gavin, in the makings of Jurassic Park III, Joe Johnson said InGen was up to no good again and created the spinosaurus and also went on to saying the spinosaurus would cause a mass extinction on the island. Seem like Trevorrow took Joe's words as canon.