Salah is certainly a respectable player, but I don't think Real Madrid would want to sign him. I am 100% sure that they will want to sign young players with high potential such as Osimhen, Leao and Kudus (Kudus is my favourite). Salah will most likely be transferred to one of the underdog teams after playing for Liverpool for a few more years. I don't think he needs a new challenge. He is a football player who has completed his career to a large extent.
Yes, I agree with your prediction. It seems that Salah is only 30 years old and still has some of his best years (or close to the peak) ahead, but for some reason it seems to me that his best period is already behind or ending now. And in any case, Real Madrid is not interested in him, which is updating its squad and is clearly not interested in buying players who will have to be updated again in just a few years.