"Karelin, when he is 46, will not be better than the current #1 (in the future, so future #1"
I wouldn't be so sure of that.
Karelin at 34, and injured, was still the best wrestler in his weight class, and was only beaten by one point in his last match.
Whats more likely, for Karelin and Rickson and the others you mentioned, is that they wouldn't have the ability to go out and wrestle several matchs in row at peak form to take the Mundials, or Olympics, etc. At their age, they wouldn't be able to go out there and bounce right back after a hard match and perform 100 percent.