So we have theories floating about Saturn having some sort of Time fruit. Perhaps awakened Tokis fruit, which allows him to send people back in time as well. And then there are threads about him fighting Luffy.
What if it's the opposite? What if his secret goal is to send Luffy back in time to acquire knowledge about Imu or something like that? After all the Gorosei are basically slaves to Imu similar to Enels priests. Get with the program or die. So all this time they may have bided their time waiting for Joy Boy, the one and only capable of defeating Imu.