Probably, the same thing would happen that happened to the all star weekend legends game.
http://www.allstarnba.es/legends/Like in All Star Game there were two teams, East and West. These legends opened the Saturday program before the two contests. This game combined the excellent physic of some players (the youngest retired) with other glories that barely can run. During 10 years it was a classic in All Star Weekend, and participated players like Oscar Robertson, Rick Barry, George Gervin, Dave Cowens, Dave DeBusschere… After year 1993, NBA decided to finish that games, because of the frequent injuries.The opposite substitute replaced the legend's game. Since 1994 rookies played in the Saturday's All Star Weekend.
IIRC Rick Barry went down again to a knee injury in a legends game.
I think a game that would be open for fit men aged 45 and above might work, but fans just want to watch legends of the game. Those guys wore their knees and hips out as professionals, many of them. I think there are guys who maybe played in college or who trained in the other sports or rigorous professions who can hang with many legends. Guys who never made it big might be able to ball at age 50 and beyond. Bring on the church league BALLERZ!
If they want a league like a D-League for older gents, that might be fun.