We actually asked that question explicitly when we did the project funded by the Social Sciences and Humanities Research Council—namely, is there not a way we could create greater innovation through the release of companies' older IP to universities, for example, in order to let students see what they could do with it? The answer, universally, was that there was no such thing as old IP.
Look at the way in which game companies have rehabilitated all their old intellectual property. Atari, for example, has just launched an iPad version of their entire gaming collection. There really isn't any notion of old IP that can just be released. It's always something valuable that they can rehabilitate. Characters that were produced 20 years ago will get a new version. XCOM, for example, a game that was extremely popular years ago, has just come out.