Well that may be Jahn, and hopefully so. But I can't help ask what spirits are behind these groups, and what battles are going on betwixt the gods.
Meanwhile, the 'powers' are involved in a political solution (without Turkey).
The idea is that the US, Russia and Iran have come up with a plan. Assad goes, and a transition government does two things: firstly they allow time for the Syrian internal powers for whom Assad was only a fronts-person, to reposition themselves. Then the new Syrian government brings in as many different cultural and religious factions as possible, to form a democratic system. With Iran on board, that covers a swag of Shia groups. With Russia, they can tell Assad to piss off.
Of course, Sunni rebel groups, including IS, will take no notice, because although Saudi Arabia will have to modify it's position, it has no influence over it's religious-extremist-spawned Sunni groups. So the battle against them will have to still be fought, except the moderates should come on-board.
The thing about IS, is that it has had little interest in fighting Assad - it has it's own agenda.