The whole situation is already an interlocking series of proxy wars, and has been from the start.
Which shouldn't be too disturbing, as the entire Cold War was an endless series of proxy wars. Those are old hat. You just need to take care that the primaries never engage each other directly, in an undeniable (we fought Russians directly during the Cold War, but always in a deniable way) fashion.
I find Turkey's position here extremely interesting.
ISIS is their proxy, in several different ways.
One is the obvious, as a proxy against the Kurds.
But they're also using ISIS as a proxy against the West, and as a proxy to spin up a Caliphate.
Turkey is enormously enjoying watching ISIS humiliate the ineffectual West, and in fact the current immigrant crisis has at least partly been manufactured by Turkey. (Which Western leaders are playing along with, furthering the humiliation.)
They're also watching what happens w.r.t the Caliphate. They'd like the concept to take off, but they don't want to be the ones to first float the idea - that's too risky.
Once ISIS serves its purpose at Turkey's proxy, humiliating the hapless West (decreasing the power and prestige of the West and increasing that of the Islamic world), and by merely continuing to exist establishing the idea that the Caliphate is now a real thing again, Turkey will crush them utterly and mercilessly.
ISIS has an Achilles heel- they're vulnerable to cohesive ground forces. If there's one thing Turkey has it's large quantities of semi-modern ground forces that are more than willing to give and receive casualties. Turkey may lack logistics, but they don't have to go far to get the job done.
Once ISIS is crushed, all the prestige ISIS gained by staying alive and continuing to humiliate the West will accrue to Turkey. As well, leadership of the reestablished Caliphate will pass to Turkey as well.
This grand plan falls apart if Russia gets their nose too far inside the tent.
I'm not entirely sure where the US stands in all this. So far we've played along exactly as Turkey might wish, but we've also been playing along exactly as Iran might wish and there will come a time when those two will come into direct conflict and I'm not sure our leadership has thought that far ahead.
Maybe we're just jaded, but your villainy is not particularly impressive. -Ennesby
If you know what you're doing, you're not learning anything. -Unknown
Sanity is the process by which you continually adjust your beliefs so they are predictively sound. -esr