Intermediate Roadmap of Oracle's ESBs : OSB and OESB
Oracle's existing service bus, now re-branded as OESB, would continue as a part of SOA suite. Apart from basic ESB patterns for routing and service virtualization, it also has useful features like Domain Value Maps, Cross References. In addition to OC4J, it also supports WLS and WebSphere. It is well integrated part and parcel of SOA stack and is seamlessly upgraded to upcoming AS11 as a Mediator Component.
However, any upgrade between OESB to/fro OSB would neither be needed nor be supported.