Yeah, given that we've had a blond Bond, I don't see hair colour as being an issue any more.
The incessant whining about Craig's hair color was IMO one of the most absurd quasi-controversies of the last decade.
I remember that Clive Owen was mentioned a lot as a possible Bond - but I'm not sure he was ever wild about the idea. I'm not sure that some of the actors mentioned, like Fassbender, will want to play Bond - he has established himself as a serious actor who does versatile roles, but any actor who gets to play Bond risks being forever identified by that role. It's a very risky move. Then again, if X-Men:First Class gets several more sequels, playing Bond may help him not be over-identified as Magneto, kind of like McKellen avoided being identified by the wide public by just one iconic big franchise role, since he played both Gandalf and Magnero.