I already know the main reason to come to Oracle Open World this year -
Prince is going to perform on the Wed party. (And if purple is not your favorite color you might enjoy Billy Joel and Stevie Nicks who'll also be there). info here
But if the deciding factor for you are actually the technical sessions, then you can now get a list of the sessions that are scheduled to run here.
Looking for the JDeveloper/ADF sessions in particular?
Most of them are under the Oracle Develop special program either in the Java and Java EE track or the Fusion Development track.
There are some others in the SOA track in the general OOW also.
See you there in November.