What is likely to keep today's songs (and any others published after 1922 in the US) from becoming "traditional" or "folk music" is the current US Copyright law, which The Mouse got thru Congress a decade or two ago.   Copyrights now extend to many decades beyond the death of the songwriter/author -- far enough that a song is likely to have fallen out of popular favor long before it becomes public domain.

This doesn't keep the songs from being sung but it does put a damper on their being performed or recorded professionally.