It seems that both(all ?) sides have the military power to take positions, but not the manpower to hold them.
Accurate?
The Syrian army has simply a lot of manpower which is not high quality. They are local fighters, sufficient to defend their villages or towns against similar forces from the neighbor village or town. But against a heavy, concentrated attack force - and Idlib has yet enough of such forces to form them - they are simply not sufficient.
On the other hand, one has to think about the possibility that this scenario was quite satisfactory for the Syrian army. If the initial attack would have failed, there would not have been much losses on the side of the attackers. So, they were, after the initial success, attacking much better prepared and much more comfortable positions behind the frontline. Most of their fighting power has been lost in many attacks against Qomhana, and behind Qomhana was a hill which was ideal for the Syrian army artillery. Then, a lot of the fighting power of joepistole's comrades depends on good prepared defenses. They have a lot of time to prepare them, and do it. Say, the main problem of attacking Qaboun is that they are encircled only formally, but have a lot of tunnels connecting them with Ghouta. But if they have taken some new villages, they had no time for constructing good defenses, thus, their defenses will be weak. An easy target for airforce and artillery, much easier than in well-prepared defenses. And the Syrian army has time - they have no problem to attack a village many days from distance, until almost nobody remains there - the population has left these villages anyway, so there is no big problem with civilian casualties. So, in this variant the losses of joepistole's comrades will be much greater, during the time of the attacks as well as during the time of defense.
What is to expect in near future?
I think it is not an accident that the Syrian army has, up to now, simply recovered the lost territory, and would not even wonder too much if they stop now. This is not what I expect - I think they will use the fact that joepistole's comrades are outpowered now to take more territory. Actually, there is information about heavy air/artillery attacks against Latamnah, and if they really take Latamnah, Halfya and Taibat al Imam would become undefensable anyway. Then, Morek is also a natural target, and that the Tiger forces have, after taking Souran, not attacke Taibat al Iman immediately, but, instead, retaken Tal Bisam North of Souran (joepistole's comrades had retaken it in some counterattack) hints that Morek is a target. There has been also information about the arrival of further reinforcements, which suggests they don't want to stop now.
But I doubt they will take much - sufficient to clarify that such offensives finally lead not to gains but losses (the last big offensive there has resulted, finally, in some gains, mainly because the fight for Aleppo was much more important for Syria, so that they have left this). But there is no reason to do more. Idlib has yet its value as a place to transfer all the fighters from everywhere, and there is nothing important or so inside. It will be the last region to attack. The exchange of Fua and Kafrya also make sense only once they do not plan to liberate these enclaves in near future. So, the question is where they decide to stop now. Morek - Kafr Zita would be a quite natural line, simply taking North Hama but leaving Idlib itself untouched. Taking Khan Sheikhun would be, instead, a signal that enough is enough, no further attacks on North Hama, and also, as a sufficiently important town in Idlib, a nice place for the Idlib government of Syria. Moreover, a chance to find evidence for the gas fake on the ground.
But who knows, maybe as well that this will be left as an invitation to attack in future in the same way, given that this direction would be the most attractive place to attack beyond Aleppo. So, leaving this as it is would decrease the motivation to attack at other places. So, time for a map:
There was a heavy suicide attack against civilians - those transferred from Fua and Kafrya to Aleppo - with 70 or so civilian casualties.
https://www.almasdarnews.com/article/angry-syrian-army-speeds-preparations-west-aleppo-offensive/ One can expect that, as a response, there will be attacks in the region West of Aleppo, a region which is much more important, in particular for the security of Aleppo, than taking Khan Sheikhun.
