Not gonna happen that easy for 2 reasons
1 - Whites are unlikely to vote for another black president so soon after Obama and especially after Trump considering the racial vitriol he's come out with. Regardless of Trump's performance the "deplorables" will either feel justified in voting for Trump (if he does well) and therefore reject any "politically correct" candidate. Or, if Trump performs badly, they'll feel resentful and still reject the "corrupt" media et all, and still reject any politically correct candidate. The best way to get around this is to get someone who fits their idea of a success (powerful white male, preferably rich with a good looking wife and kids). 61 million voters who voted for Trump is nothing to be sniffed at or ignored, and the Dems need someone who can take quite a handful of those votes back.
2 - Obama didn't accommodate black people in quite the way he said he would while he was campaigning, and in the aftermath of a Trump presidency I doubt black people believe another black person can win, or they won't believe them even if they run anyway. Most black people I've spoken to voted for Hillary because the prospect of Trump was too scary, but actually preferred Bernie.
If the Dems can get a younger version of Bernie, who can still appeal to the blue collar bible belt, they'll be onto a winner.