I don't believe for a minute that Trump will get a significant amount of black voters. He will probably get in the mid teens and Biden will get over 80%. However, the problem is turnout with that group. If black voters in places like urban inner city Atlanta, Detroit, Milwaukee, Philadelphia, etc, it will be the death knell to Biden's campaign. Biden could even get Obama 2012 margins with blacks (which he won't) but he could still lose the key states due to them not showing up in historic numbers.
Finally, someone else says it! I've posted this at least a half dozen times in the past few weeks