So I'm pretty sure I heard Savitar say, "I created myself", when Barry asked Savitar whether he was the one who created him. What if Wally is Savitar? Savitar created him and Julian. What if he was corrupted or turned insane after spending years in the speed force?

There was also an interesting bit about why only one of Iris or Savitar could survive, though I am not sure if that has to be taken literally. But when you think about it, it was the fear of Iris dying that made Wally throw the last piece of the ring into speedforce, thus liberating himself.

Edit: A second theory: Jay was the one who suggested that they throw the stone into Speed force. If Jay was Savitar, it makes sense that he wants to plan his future(past?) escape. Plus he is already a speedster.