I tried to use version 2.2 of JPA with Hibernate 5.3.1 final. I used persistence xml with such clause which should work well:

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
version="2.2">
.......
</persistence>

It does not work as there is an error like this: "Value '2.2' of attribute 'version' of element 'persistence' is not valid with respect to the corresponding attribute use. Attribute 'version' has a fixed value of '2.1'"

I looked inside the release hibernate core jar into the jpa package. There are xsd files for persistence and orm in version 2.2 but inside them the version is fixed to 2.1 - why not 2.2? Maybe this is the source of issue here during validation of persistence.xml?
If I use version 2.1 in the mentioned clause everything works well.

Hibernate jar was taken from maven: https://mvnrepository.com/artifact/org.hibernate/hibernate-core/5.3.1.Final