IGN has released a write-up giving some early insight into some visual changes in NBA 2K12.
"In the NBA 2K12 demo, the NBA Finals logo is plastered over everything, and there's an added level of pomp and circumstance to the opening cinematic. The character rosters are moving full 3D models of the players. During the game little ads pop up on the bottom showing the rivalries of the teams, and making the game look like a TNT broadcast. The fans in the stage are wearing game shirts, showing their support with a sea of team colors. It's all a lot of fluff but it's the sort of fluff you would expect when watching the Finals on TV. "