I worry about that, too. It seems as though there are fewer people interested in singing old songs, venues for traditional-oriented performers are slowly folding, and the public in general has a steadily diminishing chance for exposure to the sound of a traditional song via the media.
On the other hand, there will always be people studying the past: School kids, for starters. Since there's not a period in history that isn't documented in song, wouldn't it be nice if schools taught folk music a valuable primary source of information when studying early times? Wouldn't it be terrific if music teachers stopped to consider that "good" music doesn't always have to be from certain elite composers, and that those often took rhythms and melodies from common people. And how about the great ballad stories as a source of literature?
And if all else fails, someone will discover the sound of guitars, banjos and The Voice down the road, and get excited about discovering a "new sound."