My main project at the moment is an extensive RichFaces webapp using
JSF 2.0 and it has, in fact, a number of pop-up modal dialogs in it.
Although the full benefits of JSF 2.0 for RichFaces is still awaiting RichFaces version 3, the functionality is there, and it's primarily the performance and code simplicity that's being improved. In the mean time, however, JSF2 and RichFaces do play well enough together that I've been running it in production for over 6 months.