When the plugin is trying to start, the following exception is thrown:
INFO: plug-in started - renameFile@1.6.3 (active/total: 3 of 3)
Exception in thread "main" java.lang.IllegalAccessError: tried to access field net.sf.jabref.SidePaneComponent.manager from class renamefile.RenameFilePanel
at renamefile.RenameFilePanel.(RenameFilePanel.java:21)
at renamefile.RenameFilePlugin.getSidePaneComponent(RenameFilePlugin.java:38)
at net.sf.jabref.JabRef.startSidePanePlugins(Unknown Source)
at net.sf.jabref.JabRef.openWindow(Unknown Source)
at net.sf.jabref.JabRef.start(Unknown Source)
at net.sf.jabref.JabRefMain.main(Unknown Source)

It did still work with JabRef 2.11b3.