When you want to start using Java 5 features in a plugin, or shared component, this process must be used as decided by the Maven PMC.

A plugin can start using Java 5 features and/or dependencies when the need arises, but if there are issues that have been fixed but not released yet, the current trunk of the plugin must be released first, targeting Java 1.4. In the announcement for that last Java 1.4 version of the plugin, we inform the users that this is the last version that will be able to run on Java 1.4.

When a plugin, or other component, decides to switch to Java 5, you should use the description field in JIRA to label the versions for the plugin, so that it is clear which version runs on which version of Java. See Maven Changes Plugin for an example.