Yes I agree with you, that Neymar may not be plying anymore when the 2026 WC is held. The reason is quite basic and one of them when he often suffered injuries throughout his career and that alone made him give up and decide to retire.
Brazil we know that they are the creators of a very potential young seed, and it would be nice now that they are looking in that direction. Maybe in the last few years they have declined a little bit and can't compete anymore, they have to realize that.
Next year they will also have a new coach, the one who is in charge of Real Madrid now, Anceloti C.
I'm not that sure, Neymar is only 31 years old, so he will still be in a reasonable age to play the next world cup.
The thing is that he of course might get injured, but I don't think there is a higher chance of injury right now than what there was a few years ago, so I reckon he might still play.
We've seen Cristiano Ronaldo and Messi playing in a world cup with many more years, so it can definitely be done.
Neymar is a good palyer even when he gets old. But because of the playing style he has, Neymar can't have the performance we saw from him during all these years because he usually tries to dribble players and this needs a strong and young body which is not something a palyer can have when he gets old and that's why I said Brazil shouldn't rely on him for the next world cup.