The underlying issue is regime change. The US, Saudi Arabia, Turkey, and FSA want regime change. Russia and Iran are opposed to regime change, but for different reasons.
The primary reason for the Russian intervention was to enhance Assad's negotiating position.
There is an obvious solution. Russia has gone chest deep in Syria so let them foot the bill for a while and stew in their own juices. The US is only ankle deep in Syria, limited to providing arms to FSA.
I think it will be interesting to see if Putin, Iran, and Assad can drive FSA, Nusra, Kurds, and ISIS out of Aleppo/northern Syria.
Well there is no FSA at least in a political sense (only scattered militia groups that mostly linked up with islamist extremists and are now dying or running away with them; Nusra is taking heavy hits from Russian attacks, they have good intelligence about where these guys are, and are particularly interested in wiping out the al Qaeda foreign fighters so they don't end up back in the Russian republics or Libya; the Kurds may be opening an “embassy” in Moscow, and may be natural Russian allies to counter sunni extremism and Turkey; and once the Russians help secure Aleppo it will be on to Raqqa and Iraq- where some reports indicate they have just been invited by the Iraqi govt to conduct attacks (in defiance of US threats to cut ties with Iraq if they let the Russuna conduct military operations).
So this is one heck of an interesting time in history, things are moving very fast.
Can the Russians keep up the military momentum in Syria? Because that is driving everything else in the region at this point.