One rumor I find plausible because I have heard it from sources I have used before is that Jamie Foxx and Katie Holmes were at an event together and Jamie got a little handsy with Katie after drinking. Katie didn't appreciate it and hasn't spoken to him since.
Katie loves to distance herself from anything Tom Cruise related. Anything. If Tom Cruise walked into a room filled with people and Jamie Foxx is in the room Tom Cruise is going to go give him a hug really quickly.They love each other. Katie has known Jamie a long time. Katie isn't going to do anything that could involve seeing Tom Cruise in her future.
Jamie is perfectly happy with the "girlfriend" in his life right now and were seen together all weekend.