Neymar's absence wouldn't be a big problem in the Ligue 1 matches even if he doesn't return until then. Because PSG are still too powerful against the remaining teams in the league. Mbappe and Messi would already be enough to obtain comfortable victories in many matches. As you said Neymar is returning very soon so there isn't any problem for PSG. They will just hope for Brazil to have him playing for as short time as possible. If he gets another injury this time it might be more serious.
He is already an injury-prone player you know. PSG had to face with a serious injury for Neymar in the previous season. He missed so many matches due to this. PSG need to keep all of their players in the trio away from an injury before their Champions League matches. Otherwise the Champions League title would be no more than a dream.
Today, I read from various sports news sources and dailymail. reports that Brazil manager Tite, confirmed that Neymar will return to training ahead of their round of 16 tie against South Korea. however, he declined to elaborate on whether Neymar would be used in the starting line-up or on the bench. So, I assume that Neymar's injury is not serious if he can be sure to train with his squad.
nevertheless, refer to what you posted. yes, we agree, even if Neymar has to be absent for an indefinite amount of time. that, it will not be a serious problem for PSG in Ligue 1. even though there are only Mbappe and Messi, PSG is still too strong for their opponents in the French league competition. after all, there are Pablo Sarabia and Hugo Ekitike who can be rotated by Galtier, although they are not as sharp and good as Neymar.
however, if Neymar is absent in the match vs Bayern Munich. I'm sure PSG will have enough trouble breaking into their opponent's goal. fortunately, the good news is that Messi and Mbappe have not experienced any significant problems so far in the Qatar world cup. and I hope, Neymar really has fully recovered.