The title. Did they know that service to G-d would eventually take on a different form? (i.e. Rabbinic Judaism). They had the Torah, which mentions multiple times that the Children of Israel may deviate from the path, but did they know that would lead to exile? Just as we know the next phase of this world is Moshiach, did they know the next phase of their world would be Galut?
Thanks and Chag Sameach