It feels like blizzard keeps teasing it. First with SOD and then with the first follower dungeon having the tank be a shaman in war within.
Hard to say though as I thought dragonflight was the perfect expansion to explain how all races would get shaman, and that never happened.
I would love to see a fourth tank spec for shaman though; the playstyle was fun in SOD so if it’s anything similar I think it would be fun.