With some clubs, like the Yankees, it has reached a point where one day they will have a shortstop wearing "99." They will look more like a football team's defensive line because all of the digits under "50" will be gone.
Personally, I wish all retired numbers (except for those that truly changed the game like Robinson and Babe Ruth) were abolished, wiped clean. That's because numbers can remind us of heroes of the past. By retiring them, it actually has the exact opposite effect.
Growing up, my favorite players were Graig Nettles, Reggie Jackson, and Don Mattingly. I would actually like to see those numbers on the backs of players digging in at Yankee Stadium and running around the base paths. And I'll bet the names of those old Yankees would come up in conversation more often by the announcers as a result. You might hear John Sterling say something like, "Well, that rookie served Reggie's number proud!"
But it won't happen, of course. Teams like the Yankees actually sell tickets to walk around Monument Park so fans can gaze at the old retired pinstriped numbers. I just can't help but wonder what they'll do when they run out of two-digit numbers in 100 years.