Please, believe me when I say that I don't want this to be a doom and gloom thread. I'm not sitting on a curb with "The end is nigh!" cardboard sign.
But to be fair, "achieving destiny" isn't exactly an open ended statement. I personally believe that there are a lot of interesting ways Hasbro could take series four, even if season three ends with an Alicorn/Princess Twilight. New villains, perhaps new parts of Equestria.