If you know the past you can predict the future. This isn't always true, but this post by Doc Searls really helps understanding how the podcasting business model can evolve. If you're interested in the topic there is also a (very long) post on Ratcliff blog which, on the contrary, considers the "future" of podcasting.
Be aware you need some time to read the discussion, and you will also have to skip some flames. But it's worth reading to get a better idea of where the podcasting business can or cannot head.