I think it is a revival of sorts , but, it is a result of "how things arise from so many diffrent places" like Julie said. Roots music is popping up everywhere you look, but, I am not sure if the market is expanding.
I think here in the states it has something to do with the absence of Garcia and the Dead. When I was younger while I was listening to Deep folk and blues , my friends with similiar tastes were just listening to the Dead. Without the Dead corning the popular market for roots music others are getting more attention. My friends are going to Del Mcoury shows and buying Doc Watson albums now.