We've been down this road before...
There are a lot of variables and potential variables here. Can they authenticate that it's R. Kelly in the video? Can they identify the girl? How old is she now? How old is she at the time of the video? Can they conclusively find the time frame for when the video was made? If this girl is over 18 now and says she was a consenting adult who was role playing and they can't prove otherwise, they've basically got nothing. It wouldn't even be subject to laws around obscenity and file keeping requirements for porn because it wasn't commercially produced or distributed by Kelly. The last time around, R. Kelly was able to create reasonable doubt about whether it was him in the video, whether it was the girl they claimed it was in the video, how old she was in the video if it was even her, etc. Maybe they've finally got him now, but I wouldn't be too sure. He's a slippery son of a bitch with the best lawyers and hard to get a jury, especially in Chicago, to convict.