@cicerone imposter,
Assad is a monster there can be no lasting peace in Syria while he's in charge. He let most of the IS leadership out of prison right at the beginning of the uprising just so he could discredit the opposition. Tactically he's a bloody genius, and now he's got both Putin and Trump dancing to his tune.
The longer this goes on the more likely ordinary Sunni Muslims are going to start seeing IS as the lesser of two evils.