I'm assuming we're going to just see the same level of voting apathy from blacks that we've seen for years where there wasn't Obama on the ballot, it's why Democrats are so eager to do some ballot harvesting, they could then send out a few volunteers to get these apathetic blacks' votes in.
And when it comes to getting the black vote someone like Biden likely helps more with that than any VP pick would due to his association with Obama.
While there's also the fact that everyone's vote matters and all that bullshit, not all votes are swing votes that the parties can reasonably expect to swing a significant number of. In Trump's case he is doing well about getting a few more blacks and Hispanics over to his side, so for Republicans it does make sense to try appealing to those groups. But this doesn't change the fact that for Democrats the main swing vote that they've identified, or at least believe they identified, is white voters.
With voter apathy, that's of course a major issue for the Democrats and part of why I figure Trump will have a reliable win. The Democrats are insulated enough with their media that they aren't noticing how unpopular some of their shit is and are relying too heavily on the media's notion that a hate of Trump will drive voters to the polls, even when they've gotten to the point that it's more exhausting Democrats psychologically than energizing them.