We have to consider the situation with a "weeping eye and a laughing eye" (german saying!).
Maybe the jihadis can enter the city at night, being very carfully, but this is not a corridor. SAA hast still the fire control over the area, don't forget! In the past SAA did many big mistakes, the ar-Raqqa offensive was a disaster, but now they are doing are really great job! Don't forget the jihadis attacked with more than 10.000 men, and the death toll is around 2000+, these are the biggest losses in a single offensive in last years and I follow the news about Syria for several years. If SAA is able to close "the corridor" again, the jihads has lost the war.
About defense and mines...
I think the SAA defense was not soo bad, they hold for a long time the defense line (of course not comparable to a real good army!). But with dozens SVBIED, utilized by al-Nusra, they beat a breach in the defense lines. Even if the SVBIED don't damaged the syrian troops, it's enough to let the mines detonate in a big radius and create some crates for the ground infantry (A SVBIED can be load with 5 - 20 tons of explosive).
Also don't forget SAA is progressing in other areas, Kinsiba, the pocket near Damascus and so on.
The jihadis are massed around Aleppo und this will be their doom! The death toll was too high for a city with a long lost strategic adavantage for the jihadis. The corridor is in the grasp of a cutting pincer (SAA), the death toll to travel through the corridor will be enormous high. And last but not least...what the jihadis gained in Aleppo (not much!), they lost in other areas.
Trust me, the big game changer will be meeting between Putin and Erdogan
Erdogan is now confronting the EU, even the pussy bureaucrats in the EU are pissed off, but he needs partners and with Russia he can deal easily. Russia will make no bla bla about human rights in Turkey so Erdogan will prefer a good relation with Russia. The Aleppo offensive was also a political weight for Erdogan in the coming meeting with Putin. At the end Erdogan will turn off slowly his Sryian engagement and the jihadis will loose the war.