At some point in time, songs that started out as "popular" or even "commercial" have indeed "become" folk music. The oldest and most traditional songs we know of were once new, after all. Their composers were probably even known! But I do understand the point of view that a mere century or less isn't a long enough gestation period for everyone's taste.

Pop songs can "become" jazz much more quickly, as can be seen by the many "standards" found in Fake Books. John Coltrane created his immortal version of "My Favorite Things" no more than about a decade after the song was written as a Broadway Show Tune.