Should he remain in power ? Of course not.
Is there presently a credible and stable realistic alternative ? No.
He could potentially remain in power in part of Syria for a long time to come, but I don't see him retaking the rest of the country any time soon.
Breaking the country up seems to be an increasingly palpable and viable option by the day.
The country seems to already be broken up right now. The question is whether there's a viable (or desirable) path to put it back together and/or whether it's possible for it to remain broken up without a civil war going on.