I really dont think it will be his last fight. His post-retirement plans are centred around a hollywood career, and to do that, he will need to bring Heavyweight Boxing back to the USA, and win a few exciting big fights there, or there will be no draw or incentive for Hollywood to give him film roles.

I also remember him saying a few years ago, that he trained BJJ for flexibility along side his boxing, and would love to become the first heavyweight champion in boxing and MMA.

He has to beat Wlad first for any of his futures to happen though.
Don't let the door hit ya' where the good lord split ya'