According to the Boston Globe via Hotair the redistricting that is coming in Mass is why he is deciding to hang it up. Sorry I don't buy it. There is no way that this guy would get out of congress if he thought they were coming back into power. Face it his seniority and tenure in congress this is the guy would would stick around like Robert Byrd did and not leave until the crypt keeper comes gets him.
Could there be something coming that we don't know about yet? Even if there was lets be honest the MSM would never report it and the odds of it becoming anything more than "Move along, nothing to see here" are somewhere between slim and not ever gonna happen
UPDATE: Apparently it was the redistricting that caused him to decide to retire. I guess the prospect of actually having to go out and try to win voters over caused him such fear and anxiety that he decided just to give up.