The Zend Framework team announces the immediate availability of version 1.8.4pl1:

This patch-level version corrects a missing patch for Zend_Loader_PluginLoader that provided some critical functionality for Zend_Amf users. If you utilize that component, you are encouraged to upgrade immediately; for all other uses, the release tarball remains the same as the 1.8.4 version, and upgrading is left to your discretion.

Look for an announcement of a preview release or beta of 1.9.0 in the coming weeks. We have confirmation of many exciting new features, including the long awaited Zend_Queue and Zend_Feed_Reader components