This TP4 release is all about events.
In JDeveloper 11g TP4 there are some new features like
Active Data Service, this is very interesting push framework. ADS refreshes the ADF bindings when the data source is changed. This data source has to publish events. BAM can be a data source which can publish event.
MDS Metadata services, Customizing pages is more explained.
New features of Soa suite 11g
Event delivery network, A new Enterprise console and Business Rules is more explained and off course the J2EE edition of Oracle BAM.
There is a lot to blog about especially about events and how to use this in ADF, Soa suite and in BAM.
So check this blog and other Oracle bloggers for all the new details.