Even Pep could get fired if he stays out of top 24, I know that he won so much with this club and it would be very difficult to fire him, they probably won't, but there will definitely be a serious consideration to fire him. Why would they keep him around if they think that they are going to end up with bad results like this? So they need to realize it's doing fine before they do anything about it.
If Manchester city fails in the UCL this season then perhaps Pep will remain safe. Because he also just made a contract extension for two seasons. And I'm sure one bad season won't get Pep fired. But consideration of firing him may be there but the possibility is small. But perhaps the current PSG coach, Luis Enrique, is in a difficult position. Because if PSG fails in the UCL this season then I think his position as manager will really be threatened there.