Elba will be a fantastic Roland, and I would love him or another POC (or woman, or both) as the Thirteenth Doctor on Doctor Who. But I'm not sure how I feel about a black James Bond.
Bond stands for the last real bastion of the power of the British Empire. He is the ur-White Savior, the epitome of the white male power fantasy. He drinks, he fights, he spends. He is awesome, but decidedly a problematic figure. For all his charisma, he is emotionally stunted, misogynistic, occasionally racist and casually brutal. A good Bond film should function both as a celebration and a criticism of these figures.
I said the same thing in a discussion of whether or not Galinda in Wicked can be a POC; with a character like this, who represents and serves as part of the hegemony, you may lose something by color blinding a role with such cultural and political baggage. Then again, this depends on the idea that future filmmakers will continue focusing on writing smart, mature Bond films instead of just guilty pleasure movies. If not, if Bond is gonna just keep frigging and fighting, Elba is welcome to the part, but he deserves more than that.