Verify if move to a more reactive approach for event propagation and loose coupling between components.
For example, verify (for what it's possible in Java, without a full rewrite in Scala)
An innovative frameworks like Play have chosen for its new major release (2.0, released in March 2012) to do a full rewrite in Scala BUT with full compatibility even with Java (and Java 8 should have the same features too ...).
Last, another interesting point to explore (but again mainly for Scala, or using Akka even from Java) could be to use Actors (local and/or remote), even for events ... just as idea.
Many other interesting ideas for a more "complete" approach to make applications from Eclise E4 (extension points, mapping controllers to URLs, etc), for example some info here:
and of course even from Griffon (in from the Groovy side).
At the moment this issue is only a pleceholder to share in the same place ideas and links on this subject ... so as always comments are welcome.