There's no reason Bond shouldn't be black, though. There's no canonical thread that directly links Sean Connery to Daniel Craig other than a shared name and general theme. If we were to stick strictly to the terms of the books, Bond would be about 116.
Connery was identifiable as Fleming's Bond and the films were based on his writing. The films which followed Connery have been Bond in name only. His next incarnation could easily be black, Asian, female or a dog.