The song itself isn't new, it was written probably more than 8 years ago by Mark Lowrey and Buddy Greene, (who are usually featured on the Bill Gaither Homecoming shows)- I agree though; "Mary, Did You Know?" is one of the great Christmas songs, it's been recorded by artists ranging from Kenny Rogers to Clay Aiken.
I heard Mark Lowry talk about on the Gaither Homecoming Christmas show a year ot two ago and was surprised that he and Buddy Greene had written it. The first time I'd ever heard it was about 7-8 years ago on my way to work. Kathy Mattea was singing it and I pulled off the road to listen. It's a wonderful song. I really only meant new as compared to other Christmas favorites that have been around for 50-60 even 100 or more years.