Future of Java Server Faces...?

Struts is a Java web application frameworks. The JavaServerFaces defines a user-interface framework for Java web applications, and this does result in some overlap with current Sun ONE Application Framework and Struts functionality. However, JavaServerFaces is distinguished from the Sun ONE Application Framework and Struts because it is focussed on providing a component model for the user-interface. Sun ONE Application Framework extends the Model-View-Control architecture using a J2EE-based design pattern that comes with an extendable but ready-to-use base implementation. Struts encapsulates the user-interface more at the form or page level.

The ideal scenario is to allow JavaServer Faces technology to work with Struts and Sun ONE Application Framework. This means that future Sun ONE Application Framework-based or Struts-based implementations would use JavaServer Faces components for component-level functionality (rendering, events, etc) within a page, but continue to use the theirown application model for dealing with higher level functionality, such as forms and actions.

The best answer is probably from the lead developer of struts:

http://jakarta.apache.org/struts/proposals/struts-faces.html

The interesting thing is that the lead developer of struts is also the specification lead for Java Server Faces and he says "many JSR-127 expert group members consider high quality integration with Struts to be an important success factor for JavaServer Faces to be accepted".

I think the simple answer to your question is that Java Server Faces will provide a unifying UI component framework for web applications leaving frameworks such as Struts to enhance that framework.

At the moment Java Server Faces is still under development, while Struts is a mature technology. The link I mentioned above recommends using Struts for applications with short-term schedules and some experimentation with JSF for longer-term schedules.