If you look at the main stars of PSG, Messi-Neymar, and Mbappé we will see that all three of them are going to go quite deep in the World Cup with their teams.
So, I think PSG might actually encounter a little bit of problems with the restart of the club competition.
I dont know if you are aware that Messi is injured or not. But he is determined to give his full potential to the national team, it doesn't matter if he gets injured or not. I dont know if he intends to take time off or not. But it doesn't seem unlikely that he will get injured.
Neymar already had an injury. He is playing for Brazil but I dont think he has made a full recovery. I expect Neymar to take some time off after the World Cup. Mbappe will probably stay healthy because he is not that old. But he can be fatigued.
Most chances PSG will not have any problem if these all three stars will be not available for the first two or three matches after the break because they have enough strength for having win against their opponents into Ligue 1 without them even most chances all players will be available and give their best for the club but still they have nearly two months in start of Champions League and Ligue 1 is surely not problem for them even if they have just one or two players completely fit after the world cup.
There is no doubt Neymar will be not available after the end of world cup until he fully recovered but most chances Messi and Mbappé both will be on and give their best which is also enough for the club for retaining their top spot in Ligue 1 table.