I dont think this is true. Swing isn't going to be replaced. Just that the way the JavaFX applications are written would be different in JavaFX 2- More of java like syntax than the JavaFX Script. From what I know with JavaFX 2, UI created in JavaFX can be more easily integrated with Java applications.
JavaFX isn't part of the Java 7 roadmap, but I think it's too early to say anything about Java 8. My impression was that it will be a lot closer aligned to Swing (more like a big Swing update than a separate API, actually), so it may become part of the JRE at some point.
Swing will not be removed from Java anytime soon. It would break too many applications if they all of a sudden require an extra library which isn't supplied. That's the drawback of public APIs - once something is in there it's almost impossible to get it out without breaking existing code.
As for using JavaFX as the main toolkit, I don't think it offers much over Swing. Last time I checked Swing had more and more powerful controls than JavaFX (JSplitPane, JTabbedPane, JTable come to mind). That would mean I would need to create these controls myself (or find a JavaFX library that has done it for me) before I can use them. I would keep using the "old" Swing controls, and I don't think I would be the only one.