Warren Moon is currently the only black QB in the NFL Hall of Fame.
The interesting question is, who will be the second? I would probably say Russell Wilson, as I think he is on that trajectory, but some will always dismiss the one ring he has, giving the D and Lynch all of the credit, but I have never bough into that. Wilson, by my eyes, just looks like a HoF QB.
Having said all of that, while he shouldn't get in, I could see the media voting McNabb in, to avoid the cries of racial bias if he doesn't get in (which would be inevitable).