For sure , since the president is at the end, no big stuff will happen until the election is over. Fairly sure that this is a proxy war between sunni and shia , (daesh/wasabi groups vs Assad). I don't think there any really strong opposition groups who are secular or pro democracy , to speak of. Just after the protests started, at the beginning, this was co opted by the sunni backed emirates.
Maybe the Russians will pull out because of financial reasons, just like in Afghanistan, but the Iranians are in it and that means allies.So they will probably stay. My question is how far will the US back the Saudis? Do they stand to make a lot of money from the armaments ? If so, they will let this go a long time without intervening. But if it looks like it starts spreading to other parts of the world, then I think chances are good , she'll send in a force with a smattering of international players.