It has been suggested that not too many of 'todays' songs will become part of the tradition.I don't profess to have an answer to that question, but I do wonder how many songs from 'history' didn't survive the 'traditional process'. How many songs/tunes died on the way to present times. Given that we have better information storing techniques today I wonder if more songs, that in the past would have died a natural death, will survive beyond their 'sell by' date. May be the 'tradition' was a filtering process.
chris