Things have really heated up since I first started posting about this.
Microsoft has announced Silverlight, an RIA development framework that's supposed to out-Ajax Ajax. It's been less than a week, but Silverlight has opened to rave reviews.
Not to be outdone, Sun is striking back today with JavaFX, a RIA framework that is also intended to out-Ajax Ajax. Thus spake Gosling (who should know): "You get much more dynamic behavior. You get much more advanced APIs that you get access to."
More Java-y goodness. I'm hoping now for a response from Jesse James Garrett and the open-source camp that's been championing Ajax -- and when I see it I'll post about it as GvM - part III.