Now, Tolkien was very religious so this most likely is not true, but I was thinking that perhaps these cults that were formed that outlasted Sauron could maybe be religions of our world today. The only reason I think that is the whole "outlasted the fall of Sauron" thing.
This also doesn't sound like Tolkien, in both his writing style and his personality, but perhaps he was insulting Eastern religion by having wizards go east and set up cults?