Yesterday, Apple released OS X 10.9.5, the fifth update to Mavericks.
Interestingly, this update appears to contain the exact same version of Mail.app as the prior version of OS X so the Delete2Archive plugin should continue working without any issues.
However, to avoid any confusion for those looking for a version of Delete2Archive that explicitly states it is compatible with the latest OS X release, I’ve made a new zip file for 10.9.5. It has the exact same contents as the 10.9.4 zip file, just a different name. Follow the installation instructions and download the new version of the plugin from the Delete2Archive page.