If Messi and Neymar both leave PSG at the end of the season I think this would leave a very negative effect on PSG's overall performance. I know that PSG haven't been much impressive even with this trio this season however the reason is Galtier's strategies mostly as it's seen clearly. The right manager for the team would be a big step forward for the team about making their dreams come true especially about the Champions League title.
Messi and neymar have been stating to leave from the PSG in summer. Neymar's agent has been getting some offers while messi itself was also confuses about which club that will become next next club. The chance for messi and neymar to leave from PSG are very high at this moment consider if there was no another talk between neymar and messi with PSG.
As far as i know if neymar and messi don't feel satisfied to stay even longer in PSG. I see that if the decision that already taken by neymar and messi are good decision now.
However in case of seeing these two very important players leave the team even the right manager would have to deal with some serious problems about achieving their biggest goals. I wonder who would make a new trio with Mbappe in the attacking line.
What problem? PSG had a bunch of money. Searching new players to replace messi and neymar will not become hard tasks to be done. PSG has been tageting several players include osimhen from napoli. It's likely that if PSG will be also increasing its offer to the napoli for osimhen.
The problem is, if PSG is not having a good coach right now to handle the team. that was also making the club has limitation to improve its performance compared with this season. PSG needs to use its money wisely.