A release candidate version of Geb, 4.0.-rc-1, has been released and is available from Maven Central.
This is a candidate for a new major version that will bring integration with JUnit 5.
Please note that the way Geb integrates with test frameworks has been revamped and extracted into GebTestManager which helped to remove duplication and will make integration with test frameworks easier in the future. Introduction of GebTestManager required base test classes that Geb ships with to be changed in a backwards incompatible way - you should not be affected by that unless you overrode methods defined on these classes.
Please try out this release candidate and provide feedback. The plan is to do a final release in two weeks unless some major issues with the release candidate are discovered.