To me it would seem a bit silly for Messi to play in the next world cup, he has the chance to retire after he won the world cup, and now he can play a bit more to make some extra cash, plus then he will be able to continue making money by doing ads and things like that.
Playing the next world cup would not bring anything else to him, even if he wins it
Maybe Messi won't get anything in the next World Cup, but what some users here have mentioned is that Messi is still Messi, a football superstar who has become the idol of footballers all over the world and that also includes Argentinian footballers. Messi won't get anything, but young Argentine national team players will get something very valuable in their lives, namely playing football with Lionel Messi. It is possible that in the 2026 World Cup there will be several new faces in the Argentina national team and we can confirm that their average age is 20-29 years which means they are football players born in 1997-2006 and it is certain that they will be very motivated for every match.
Definitely if Messi happens to participate in the fort coming world cup, he may not be aiming to get anything really big but then his presence in the tournament alone will really mean a lot to his country and the entire tournament as a whole as it will cause some side attractions, for a football idol participating for the last time in the tournament.
Most of the young Argentina players would be delighted to have ever played with such a big star at the same time in a tournament. His contribution to the team as an experienced world cup player will as well be off great benefit and importance to the team, and I'm very sure the fan base for his country will be bigger than usual as many more people would want to witness him play.
It going to be more beneficial to the tournament, his team and his country at large than it will be to him, but then on the long run it will be narrowed down to him as an achievement in his football career, he will be forever regarded as an idol in football both nationally and globally. So I don't think there's anything silly about him participating in the next world cup even if the achievement wouldn't be for him but for national interest I think it's worth it.