Good News!! This is one of the primary goals for JSF 2.0, and the component libraries projects are starting to communicate and plan on testing interoperability between each other.
IceFaces, RichFaces, and Primefaces have discussed this, and while formal interop has not started, it is planned. However it should be working ok, any issues you find please let us know.
Thanks jay for your reply. Yeah! It's really a good news.