I would say, if Neymar doesn't suffer any serious injuries this season, we will see the best performances from the trio of Messi, Neymar and Mbappe next season. Neymar and Messi's chemistry was excellent at Barcelona. If we see this again, PSG is undoubtedly the favorite for the Champions League. Because PSG has talented players like Mbappe in the attack along with Neymar and Messi. Who are capable of breaking any team's defense.
Injuries are always big issues of Neymar since his transfer from Barcelona. Usually it hapens after winter holidays when players get relaxing time and sesson goes next to more serious time. Neymar does relax too much and it can affect his body too. Tighter intensity in second part of season is part of issue but main one should come from Neymar.
Naturally, human body get worse when they are getting older. Neymar can not avoid this process. His body will need more time to recharge, recover from matches and trainings. So if he won't change himself, he will surely get more injuries in next years, not less. If he gets more injuries, his performance will be worse.
Actually, Neymar is good but ManCity doesn't need him at the moment because has bought Haaland. As you said, it will be a conflict of interest for the team. Maybe Neymar isn't compatible with the Gartier scheme so they want to sell it. but Neymar is still comfortable, he won't go because no other club wants to pay him a high salary, maybe if Neymar has to go, Hollywood is good because his acting is good also.
Manchester City has a tactic that helps them to play well and not actually depend too much on a single player. In big matches, absence of De Bruyne ie. can cause issue but in general and in non big matches, they can play well.
They don't actually need Neymar to improve their quality. In recen lt seasons, they shown they need a classic striker like Kane and Haaland to find goals when their whole system without a real striker fail to score goals. Neymar is not that type of player.