Had a change of heart. Doing all of the package renames now rather than waiting for Java 9. I wrote:
There is the possibility that changing the entire name of a project could be considered a non-compatibility-breaking change according to semantic versioning...
I'm choosing to believe this is true and am renaming projects and modules without incrementing the major version number. I'm using japicmp to verify that I'm not introducing binary or source incompatible changes.