DG1-
I was talking to my favorite TPA US Airways Club rep about this. Their official policy is that we don't have to get you once you get on. Often on pretty full flights that load right up to departure time, the agents won't go all the way to the back and move someone up. If everyone boards and there still is some time, the agents will, but that is not policy, as they don't want to get FFs mad if the flight is ready to go so the agent can't move the guy up. I too have been moved up plenty of times. Another tatic is to show the FA your CP card, if there is a First seat and you couldn't get upgraded, and she/he will probably say go right up!
CP