The distribution of new Java versions is already decoupled from tzdata updates.

If you want to update your tzdata then you should use the tzupdater tool that is shipped with Java. This has been updated to support JSR-310. If you want to perform the updates then this is just a commandline tool and can be integrated into chef/puppet etc. as needed.

There was discussion during the development of JSR-310 about the inclusion of Java library methods to update a running JVM. There are a load of "not obvious to a developer" things that happen if you do this and it was decided the technical complexity and potential confusion outweighed the benefit of implementing it.