Won't happen on Obama's watch as doing so will mean a direct response from Russia.......Obama won't chance that unless war with Russia would mean another term for him....and that's not of interest to him.
The US agenda is STILL to replace ASSAD.........Like they did in Libya and Egypt when neither leader would support the Global Agenda for the Mediterranian .........that is at the heart of this.
Unfortunately people everywhere are war weary with Syria, refugees and the like... so I won't be surprised if a coalition doesn't in time pull this off anyway. Even the Muslim countries want this settled one way or another.