He'll be 37 years old by the time he signs a new contract, so his next deal could be his last NHL deal. But if Boston can get the money right - somewhere in the area of his current annual salary of $6.125 million - it wouldn't be out of the question to see him return to the Bruins.
Marchand served Boston well as their leader on the ice and off of it, and although he probably would've wanted to spend his entire career with the same team, he could, in theory, win a Stanley Cup with the Panthers, then find a way to come back to his first NHL home.