the best way to transition assad out was always to let him transition himself out, which is what he was trying to do in the first place; the thing that created this mess was an attempt at a syrian constitution, which was vehemently opposed by the saudis as an increase in democratization in the region.
that's right. that's the fucked up reality: this war was launched to prevent syria from transitioning to a democracy.
the russians don't want him there either, and will be helping him transition himself out as soon as the territorial integrity of the country is secure.