Let's not get too carried away here, there's a long, long way to go yet...
This announcement relates to a "prototype" developed by Oracle. This prototype is not the solution. It is a purely interpreted version of Java (and JavaFX) that neither runs at acceptable performance levels nor will be it be accepted by the Apple App Store for iOS.
It includes code that covers many of the areas that need to be ported but what is lacking is a full AOT Java compiler that will be essential to getting JavaFX apps deployable to mobiles and tablets. An OS such as iOS (and WindowsRT) does not permit executable memory meaning that a JIT compiler will not work (hence the interpreted-only Java in the prototype). The only way to get Java/JavaFX on these platforms is to fully compile the Java source and while this prototype will greatly help in achieving this, it will be left to an enormous effort from the community to bring this technology to fruition.
Oracle have not (and may never) commit to a GA release of JavaFX on mobiles and tablets. They are completely relying on the community to drive this port.
It is up to Java and JavaFX developers outside of Oracle to pick up the ball and run with it from here. Only time will tell if there is either enough interest or expertise in the community to ever make this happen.
"*Let's not get too carried away here, there's a long, long way to go yet...*"
...YES....but...the right way! When JavaFX get's ready for the Mobile World, then all the other "jQuery Mobile", "Sencha Touch", "Zoey" ... are obsolete from a Java Developer point of view !
Then JavaFX is many cases the better choice !!
To be ready for Mobile, Fat Client(WebStart, Applets) and [JavaFX goes Web - Render JavaFX to HTML5-Canvas?|https://forums.oracle.com/forums/thread.jspa?threadID=2499234&tstart=15] ... then...this ist the first Java based GUI language who is the real eyecatcher of the world !!
Well why exactly can't they use JIT? It seems to convert it to the DVM the same way as Java code does for the JVM. I heard that the issue with Swing/AWT was because of native code and how it would run FOR GUI. I don't know how other code runs on mobile, but who knows.
The ENTIRE FX library is now OPEN SOURCE, they just announced that.... OpenJDK has been doing an amazing job, and seeing as I'm running the beta builds I'm happy thus far. Sun also has a port going for Java on mobile, so I don't think we need to worry THAT MUCH about "performance issues," if anything performance issues might happen right away, but then be fixed pretty quickly. I have faith that we will be seeing some amazing FX apps out :).
Well hold your breath cause they might just talk about JME or some new "exciting" development on the Oracle ADF Mobile front (http://www.oracle.com/technetwork/developer-tools/adf/overview/adf-mobile-096323.html) like they did during JavaOne 2012.