I think black turn out will be much higher in 2018 and 2020. However, they don’t be voting D.
I’m not quite that optimistic; I assume the best case is higher percentage for Trump along with low black turnout. Only so many additional Trump votes - but a better percentage because of low turnout, because of people not wanting to admit to themselves that they want the Republican to win. So, lots of “half votes” for the Republicans in the form of not voting at all.