There is nothing to verify as Point Defiance Zoo has never once stated that they were even considering sending any of their elephants to any kind of sanctuary.
The zoo's website has updated information on their level of elephant care:
Elephant Care - Point Defiance Zoo & Aquarium
Here is an article from 2015 that contains information stating that Point Defiance Zoo would consider "rhinoceroses" after the elephants die. On multiple occasions in the past the zoo has declared that rhinos would be an option (possibly Greater One-horned) in the future, but that the remaining elephants would see out their lives at the zoo. With Hanako now deceased, Suki will live out her years at the zoo.
Popular zoo elephants likely to get harder to see in future