Since he is a CURRENT hall of famer, if tommorow he decides to return and fight Vitali Klitschko would it be the first time ever that a CURRENT hall of famer fought for the Heavyweight championship of the world, or for any championship for that matter?
George Foreman
Ray Leonard
Foreman was not in the Hall when he came back because the IBHOF didn't exist yet. Leonard did not challenge for the World title when he returned. Camacho may have had a belt, but it was JC Penny valuable.
I don't think any man who has been inducted into the HOF has fought for a major title, it's not the easiest thing to do considering they have to be retired for 5 years before being eligible to be in the HOF.
The first induction class was in 1990.
Foreman was inducted in 2003. Leonard was inducted in 1997. He fought Camacho that year, a few years before the induction but after his selection had been announced. It was for a minor sanctioning body title.
Fenech and Nelson did fight long after their inductions (Fenech was inducted in 2002, Nelson in 2004), but they didn't fight for a world title. They just fought each other last year.