Khans of Tarkir is not too terribly far away, now - it's nearly July, which means only a couple more months until a brave new block starts. San Diego Comic-Con begins July 24th, and with it will come the usual Magic panel and our first details about the Mongolian-themed block's story. All we know thus far: Sarkhan has come back to his home plane for one reason or another; and the death of all the plane's Dragons has some significance. But there are many ways such a plot setup could play out. Here are some of them:
Sarkhan's chance at redemption. The quintessential wild card planeswalker, Sarkhan started out unaffiliated and basically morally ambiguous, with no inclination to use the power of Dragons for good or evil but simply for its own sake. Then he came under the sway of Bolas, but the story took pains to show he wasn't in his right mind when he did so - his second planeswalker card was even called Sarkhan the Mad. As Bolas's lieutenant he was responsible in part for the release of the Eldrazi and the doom of Zendikar, but it seems he's since cleared his mind, and mass Dragon death is something Nicol Bolas is very heavily associated with, having orchestrated the extinction of the other Elder Dragons in order to cement his power. So no doubt the ancient planeswalker is going to meddle in Tarkir's affairs somehow - and it will fall to Sarkhan to defy him.
The Dragons are back and not picking sides. For all of my suspicion of Bolas's involvement, the fact of the matter is the war chiefs of Tarkir were culpable of killing all the Dragons themselves long ago. Previous descriptions of Sarkhan's home plane said the Dragons were "hunted to extinction," meaning less a war than a massacre. It's not hard to see why Dragons rendered undead by some means or another would be very eager for revenge on the descendants of their murderers.
Sarkhan plays politics. The perpetual war that Tarkir is consumed by obviously must have distinct sides. And it doesn't seem to be the kind of place planeswalkers visit very often. Sarkhan's return changes things. Some of the factions may be suspicious of the prodigal native. Some may support him from the outset, and welcome the strange kind of progress he brings. All of them want to court him for his raw power.