I don't watch Doctor Who but the hysterical cries for a female one in certain circles makes me wish they won't get one.
I say: always get the best person for the job. If that's a woman, black or gay guy, great. If it's a white guy, that works, too.
That being said I all for Idris Elba as Bond, because he, the person and actor, is fucking awesome. So I basically decide those things from case to case.
In general that means that of course James Bond can be black. Should he be, because it's time or whatever? Not necessarily.
You mustn't be afraid to dream a little bigger, darling.