I just read my x-play app and they had an article about a new mode in 2k12 called NBA's Greatest mode. It's desciribed as a mode that "will allow players to reenact the greatest basketball games of all time, with classic teams made up of old timers like Michael Jordan,Larry Bird, Magic Johnson, Kareem Abdul-Jabbar, and Dr.J."
The article also states that "You'll be able to pilot 15 historic NBA teams, complete with tiny shorts, high socks, and afro hairstyles galore." They also say that you can put up the throwbacks against the current teams, but couldn't you do that in 2k11? Sounds like an interesting feature can't wait until October 4.