Both Americans who retired at the last American tournament of the year?
I know they are both Americans but the point is, it makes sense that a big player like Federer would want to retire at the end of a season rather than in the middle and wouldn’t choose a smaller event to do it. For example, Sampras' favourite tournament was always Wimbledon and yet he chose USO to retire. Perhaps USO also made more sense since he was an American as well. Sampras announced just before USO unlike Roddick who did in the middle of the event. Federer, I feel, will announce much before his actual retirement as he’d probably like more attention from his fans and in general going into each tournament that year.
2013 might be a bit too soon for him but if he doesn’t win any titles (Masters, Majors etc.) then ranking won’t matter as much, though they are directly connected. From Olympics and on, he’s taken one too many beatings in succession. The most unfortunate event was when Nole couldn’t win Cincy otherwise it would have been a series of losses to Andy, Nole, Berdych, Andy, Del Potro etc. – the current generation. He can still win WTF and make up all the recent losses and perhaps get motivated a bit more for next year, which he will need, but if he sees another loss here, can’t say he won’t be seriously thinking about it at year end.