Kerry will go back to being a back bencher in the senate. He like his life that way. Not too much work, he could go off and enjoy his life of wealth and luxury. No, he's not going to take up the "reins of leadership" in the senate. His whole life was aimed toward the presidency. He will NEVER get that chance again. He'll go back to being the absentee senator from MA.
..and you forgot, a "prized Senate Fench Poodle" for ThereeEEEEEsa to walk around with. :)