Under normal circumstances a bill that passed with a huge "veto proof" vote would seem like an easy thing to override. But in this case, no one in the legislature wanted this bill. The whole thing is up to Mike Madigan. He bullied the whole legislature into voting for this thing. The antis did not want it at all, and the pro-carry legislators did not like the terms of the bill. Unless Madigan puts the screws on them again, I don't think the governor's veto can be overridden. It is a very peculiar situation.
It will be interesting to watch it play out. One has to wonder how much of his political capital Madigan can afford to use up on this issue mostly against his own Democrats, and in both houses. I suspect the so called "cliff" is probably prefered by a majority of the antis to a LTC bill, and that is the way they would let things go if they had their choice in the matter. That way they can avoid dealing with the issue and being forced to vote for something they really hate, and let the courts sort it out.