Probably no vacuum. Assad will simply take back control of the areas we used ISIS and our rebels to wrest away.
I remember the war harpies and Israel-firsters telling us that ISIS was now our friends on Syria. Hence we were killing them in in Iraq but friends again for the Syrian CLOWN HOUSE.
Deploying troops as tripwires and pawns for Military Complex Inc. is evil. So is the crypto-trash that logs onto FR to support it.