I don't see podcasts as an alternative to radio, but just the new radio. Like how Netflix, Amazon Prime and Hulu are just the new tv. Perhaps this is because I have always listened to a lot of NPR podcasts, such as This American Life, which are also broadcast on NPR radio stations. Of course, I also listen to a lot of other podcasts, some by people who mainly do podcasts, and quite a few others affiliated with some publication.