I did some stats on Bond. Because I'm a nerd.
The youngest Bond to date was Lazenby at 30. While he may not have been a great Bond, I don't think any of the criticisms about him related to his age. But 30 would be as young as I'd go unless they go for a completely different feel of a rookie Bond or something. Which would kinda defeat the purpose of having the cool, confident, experience of the character that we all know.
The oldest was Moore at 58. I think most of us would agree that he was too old for the role by the end, he got the gig when he was 46. Not really too old then, but should have quit after one or two films probably.
Connery (not counting Never Say Never Again) went from aged 32 to 41 which is probably the perfect age range.
Dalton was 41 and 43.
Brosnan went from 42 to 49. He had the looks of the role. What a shame his films were so crap.
Craig started out as one of the younger Bonds, at 38, behind only Lazenby and Connery. But he was 53 by the latest one, which is actually the oldest Bond to date except for Moore.
So I really think they need to cast someone who is 30 to 42. So, Elba at 49 is well out of range. Even Tom Hardy is too old (and still, urgh!). Hiddleston will scrape in and wouldn't be a bad shot. Madden is 35. Never thought of him for the role, but it mightn't be a bad casting. I think going for the slightly less known actors is probably a better idea. I think it is a bit of a cursed chalice for anyone who gets it though. A lot of actors would probably veer away from the role.
I have zero issue with a black Bond though. It would screw with the continuity set up by Craig's Bond, but there was never much continuity anyway between Bonds anyway. Eg, it was never suggested that Craig's Bond had been married to Tracy di Vicenzo back in 1969 (when Craig would have been just a baby) and she had been killed by Blofeld. [As an aside, I remember one interviewer asking Brosnan about how both he and Bond had lost a wife and did that give him some extra affinity to his character - jeeze, what a horrible question to ask someone!]
Anyway, they're my rambling thoughts. Maybe we should take it to the Lights Camera Action section of the forum though