In early 2008, Oracle allowed you to enable WebCenter 11g and SOA 11g Tech Previews through the Oracle JDeveloper 11g Technology Preview.
At this point, mid-2009, this is somewhat outdated. The actual WebCenter 11g release (not available for download by Oracle) has quite an enhanced environment, features, etc. I don’t know the timing details exactly, but I imagine that the tech preview was put together before the BEA acquisition decisions were finalized and certainly before they were fully integrated.
WebCenter 11g should be a fantastic product taking the best of many Enterprise 2.0 products and services that Oracle has either acquired or partnered with.
Stay tuned for more information as releases get closer.