Trying to get back to the OP's question.
If it had been phrased
"Is traditonal song collecting finished?" A fair question.
I would say probably yes.
There might be a few singers who have one or two gems that have never been heard before, and have been handed down through the generations but, with the prevalence of global communication available nowadays, I find it unlikely.
The days of village communities where people seldom travelled more than 5 miles from the place that they were born are long gone. (apart from Stoke, obviously!).
Yes, there might be undiscovered regional variants of already collected songs. as yet undiscovered.
But, thats probably it.
But, reading the original question (as writ), it just re-opens the bun fight that happens on a regular basis here.
It's odd that these discussions don't happen amongst musicians.
An example. I wrote a tune for a dance side in 1988 (in a quasi Traditional idiom).
10 years later, I heard someone playing it in a session. Asked the chap what it was. He said it was ages old, and he'd even changed the name! Have to admit, I was secretely pleased. Have heard it on numerous occasions since!
Maybe it will still be played in 100 years time. Now that would be nice.
All I am saying is that everything was written by someone once upon a time.
Therefore, everything will become traditional one day. We're just arguing about the length of time.