Royal Pony Sisters Origins Post S4?

So, we’ve finally gotten to see three of the most iconic events in the show brought to life : the battle between Princess Celestia and Nightmare Moon; the battle between the Royal Pony Sisters and Discord; and finally, how the sisters found the Elements of Harmony. Now, my personal head canon was that they earned their cutie marks when they found the Elements, but clearly that head canon is now wrong. However, what are we left with to explain where the princesses came from and how they earned their cutie marks? If we go strictly by what we’ve seen in the show, Hearth’s Warming Eve, their was a time when the Pony Sisters did not exist. We also know they had nothing to do with creating the Elements of Harmony. In fact, they were lucky to find them and, in essence, stole them from the Tree of Harmony-albeit for a noble purpose. My feeling is still that they were not born alicorns and attained that status just as Twilight and Cadence did by performaing new magic or helping society in a profound way. In their case, it must be linked to taking over the raising of the sun and moon from normal unicorns. My thought is that an event occurred that prevented the unicorns from raising the celestial bodies and the sisters had the key that allowed them to do it, and thus save Equestria. This theory will be proved, or not, as the season moves foward, but I do hope the writers deal with this facintating and by no means settled topic.

One other aspect of the season 4 premiere was puzzling and that was seeing Celestia and Luna looking exactly as they appear in modern times. One would suppose that they would appear younger the further back in time one went, but clearly the writers decided not to do so, if they even considered doing it at all. Perhaps even more puzzling than their physical appearance is that they were already crowned during Discord's reign. The implication of this is that Discord perpetrated a coup against the sisters and they were forced to regain their kingdom by force using the Elements of Harmony.

As Princess Celestia herself related in Return of Harmony Part I, "he (Discord) ruled Equestria in an eternal state of unrest and unhappiness." She goes on to say that she and Luna stood up to him, but nothing explictly states that they were the former rulers of Equestria. Based upon the evidence in the show one may as likely assume that the sisters rose up against Discord and were than installed as co-rulers. Without more clarification from the writers it will be difficult to say for certain.