With Danny Ainge at the helm, I do not believe for one second that ANYONE on this roster is safe, including Pierce. I'm not saying Pierce will be traded, but I am saying that he, like every player on this roster, is a candidate if Danny felt the right deal came along.
Remember: this is the same guy who, when he heard Red Auerbach state that he had two significant offers for both Kevin McHale and Larry Bird, that Red SHOULD HAVE pulled the trigger on those deals. So you think for one second that Danny wouldn't trade Pierce?
...Yes, he would if the deal appealed to him, and he wouldn't look back.