Common Design and the tenets of New World Order limit the kinds of cards we can expect at Common going forward. The whole point of this design constraint is to limit complexity and thereby keep the bar of entry for new players as low as possible while still retaining the essentially elements of the game.
But, at least in my opinion, both Khans of Tarkir and Fate Reforged have been pushing up against the constraints of New World Order more than we have seen in some time. Indeed, I would argue that simply by allowing the Morph mechanic (and now Manifest as well) at Common, signals a shift in what kinds of complexity are allowable.
Now, in Fate Reforged, we have the return of modal abilities in a cycle of creatures at Common. The presence of such cards used to be fairly routine in Magic's history; now, they are quite unusual. So while these abilities never disappeared entirely, giving players the choice of two distinct abilities when a card is cast is an unusually high level of complexity, and one that probably would have been red-flagged and then moved up in rarity save that it ties into a particular theme of the set. Additionally, these creatures also would have been red-flagged simply for the amount of text on the card, which easily exceeds the four line limit.
Choice creates complexity. Board states with hidden or hard-to-discern information also create complexity. And yet, both these elements are present at Common. Is this a shift in New World Order philosophy, or simply an oddity due to the specific needs of this block? Time will tell, but at least for now, I am cautiously optimistic about what this means for future Commons.