I agree. He is almost 41 years old, it isn't the ideal age for a footballer. Although Ibrahimovic still has the motivation to play as a player, he must be aware of his current condition. It is better to consider a new profession as a staff or coach assistant, I think he has the ability for that profession. He has a lot of experience and has good verbal skills, he can be easier to motivate Milan players.
The age factor is indeed one of the obstacles for athletes, especially in this football. There are only a few players who can survive and be consistent at an age that can be said to be quite old for a footballer, as we can see now there is Zlatan Ibrahimovic who can still compete and even become a player who really contributes to the team he plays for.
Zlatan Ibrahimovic is a motivation on his own 33 trophies throughout his carrier is a legacy already. I think he should be considering retirement although he hasn't made any official speech to this but his age is quite due for retirement. An assistant coach should be a perfect carrier he could possible switch to he the ability to fit in. Lets hope to hear from him before the start of next season