The world of version management is a moving target, just when you think you hit it on the head with a comprehensive solution for CVS integration in JDeveloper (including a built in client and a 3 way merge for example) turns out more and more people are migrating to subversion.
So our developers put the pedal to the metal and started working on a subversion integration extension. They just released a version that they call Early Access 1 - and you can get it from the JDeveloper check for update menu.
Let us know what you think on the OTN forum.
Installation instructions are here.
One thing to note is that this extension is based on a framework we now have for integrating version management tools - should make it easier to plug more versioning tools in the future.