There are already Java based RIA vendors
"Sun's betting on the ability to build rich-client interfaces using less code than programming in Swing, meaning simpler and quicker programming"
Why would Sun be betting on JavaFX to deliver rich-client interfaces, there already exists several very good products for producing very rich user interfaces using Java. These include Altio (http://www.altio.com) and other vendors such as Nexaweb and Curl [I work for Altio].
The key issue is that prior to Java6u10 the load time for Java was so bad that people would get bored waiting for any Application to load. So Altio, Nexaweb, Curl etc are probably only found in enterprise applications where users will spend long periods of time using the application.
NOTE: this is my opinion and not that of my employer