UPDATE: See the demo video: http://www.youtube.com/watch?v=A2Gy5QPeGGk
RichFaces community is complaining about complexity of maintaining namespaces through the JSF projects 
as the sample could be following project file:
It is very hard to maintain namespaces through project.
What are current options when using JBoss Tools?
- modify Facelets file templates for creating new files and list all favorite namespaces there
- use autocompletion of detected namespaces (write xmlns:xyz="..." and autocompletion will offer you available namespaces)
But both of the solutions are not as straight-forward as it could be.
Tools could help and store the preferences for namespaces,
so user would need only to start typing tag with prefix of the namespace (e.g. <a4j: and once he will complete the tag <a4j:ajax>, the namespace will be automatically added to the root of the XML file. (xmlns:a4j="http://richfaces.org/a4j").
The information about the prefixes could be retrieved from:
- faces-config.xml generated by RichFaces CDK: faces-config/faces-config-extension/cdk:prefix
- scanning the Facelets (XHTML) files in a project and collecting used namespace prefixes (xmlns:*)