The Syrian army has established a connection with the Eastern Kurds around Manbidsh:
The encircled area is probably empty of reasonable forces, there will be a lot of traps and some suicide fighters inside, but nothing else. Who will take this area already does not matter very much. There seems to be a line of agreement between Turkey and Russia. If the forces on the ground - the Syrian army as well as the pro-Turkish rebels - exactly follow this line does not matter much. The Turks have no interest in a conflict with Russia now, if some of the pro-Turkish rebels start fighting they will not care.
This cut is a quite important point, I think. First of all, it cuts any connection between Turkey and Daesh. Of course, Erdogan no longer supports Daesh, but it is not at all certain that all the Turkish secret service and deep state follow this. So, possible secret connections between Turkey and Daesh are cut. Now, the interesting question is what Turkey will do. They may start to fight the Kurds, to take Manbidsh. I would guess that there will be some American pressure on Erdogan, maybe even Russian, not to do this, simply because the Kurds have already explained that in case of such an attack they will stop to fight Daesh and defend Manbidsh. Without the Kurds, the US has nobody to fight Daesh, which is declared to be high priority by Trump. For the Russians, fighting Daesh is also high priority, even if some of the Daesh territory goes, for some time, to the pro-American Kurds, they are clearly less evil for Russia.
So, if the Turks accept this, they are, at least for some time until Daesh is finished, out of the game. But Erdogan is quite unpredictable, and may as well ignore this and attack Manbidsh. We will see.
For the Syrian army it makes sense to move toward the Euphrat, to have a large flank with the Kurds is not a problem for them. The Kurds will be happy once they have no longer to defend this flank against Daesh and not have much forces there:
Daesh will hardly spend much power on defending these places. The next more interesting target after the Euphrat is an airbase at 2. If taken, this would allow to encircle Deir Hafer, so that it may be even given up by Daesh.