The XBee / XBee-PRO DigiMesh 2.4 version 8x4B firmware can now be downloaded:
http://www.digi.com/support/productdetl.jsp?pid=3524&osvid=0&s=378&tp=2
The product manual still needs to be updated at this time, so please refer to the release notes at the link above for information regarding the changes in this firmware.