While the ongoing civil war means any formal partition is likely many years off, the recent UN-brokered ceasefire and transfer agreement in certain parts of Syria, centering on government-held territory and parts of al-Qaeda’s Idlib Province, seems to be speeding the sectarian separation of the country.
The truce in question set the stage for a deal on significant population transfers, allowing the Syrian government to withdraw Shi’ite villagers from areas no longer defensible deeper into their own territory, while al-Qaeda was allowed to move forces out of Zabadani, deep in Syrian government territory, back toward their own power base.
The transfer both frees up the Syrian military to more successfully defend their territory, and for al-Qaeda to do the same in Idlib without worrying about a smaller force in Zabadani getting outright surrounded, and seems to be strengthening the status quo between the two.
Similar transfers, less organized, have been going on in ISIS-held territory for months, as ISIS advances inevitably lead to an exodus of non-Sunnis from a territory, while occasions where ISIS has lost territory to Kurdish forces has similarly seen the Sunni Arabs fleeing deeper into ISIS territory. As the war continues, it seems increasingly to be boiling down to a de facto split along several different lines, with less and less chance of any side “winning” the war outright. The question may simply be how long they will continue to throw troops at one another until they are resigned to a stalemate and settlement.