It look like we have a new player in town - in my opinion it will be the next RIA generation.
The canvas element is part of HTML5 and allows for dynamic scriptable rendering of bitmap images. you can read about it in here. If you'll look around you'll notice that new Canvas UI and Game frameworks emerging.

True, it's not there - we do not have all we need to build a standard application but as I can see it the existing frameworks are far more advanced then JavaFX (correct me if I'm wrong) see the below List of examples to existing JS frameworks for Canvas.