Really? With how he performed this World Cup he's far from being weakened due to aging. Messi is still pretty much powerful and a good football player at that so if you could give me an explanation as to why people infer that he's gonna retire it would be great. The same can be said for CR7. Is he retiring? Is his loss really that devastating that he'd rather just quit football instead of trying for the next world cup? I think these two GOATS are still very much strong in their own right to quit playing. Maybe these are just speculations.
Having Messi and Ronaldo leaving the game is really something to worry about, there rivalry is just unique. Messi has already ended the whole debate of who's the GOAT, no sentiment. Even if Messi retires today he'll be happy that he has done it all, what more does he need to prove that he's the greatest of all time? Let's give the guy some credit.
Age is really not on both Messi and Ronaldo's side, but I think Messi can still play in the next world cup not Ronaldo. The Portugal national team can decide to drop him and before you know it he might choose to retire. Ronaldo's speed and contribution to the Portugal national team is no longer there. He's now a shadow of him self.