For a song to become "traditional" in the sense that I understand it, it must become separated from its original and take on a life of its own. In the past, before recordings, that was relatively easy, but nowadays it is much more difficult to separate the song from a definitive recording of it. Many pop songs have proved to be long-lasting and have entered popular culture, but it is difficult to think of, for example, "Yesterday" without thinking of the Beatles' version, or "Wonderwall" without referencing Oasis. It is not just the song which enters popular culture but a particular recorded version of it.

We also no longer have a popular singing culture which allows or encourages the development of pop songs into traditional ones. With original recordings to refer back to, the idea of a "correct" version is ever-present. If people sing at all, it is very likely to be karaoke where they sing along to a version of the recorded original. Other performers may create their own covers, which may be very different, but these are consciously different versions rather than developing through a "folk process".

It may be easier for songs in the folk miliue to become "traditional", as these are more likely to be spread by other singers taking them up and performing them live. This is certainly true of a lot of folk dance tunes, which are passed between musicians at sessions and may quickly become detached from their original title and composer; many are assumed to be "traditional" in origin, and probably now meet the criteria through the way they are disseminated and the variations which creep in. For pop songs, which are known principally from commercial recordings, it seems far less likely that this will happen, but it is entirely possible and cannot be ruled out.