For MS not to trend Democratic, you are betting on the longevity of seniors in one of the most unhealthy states in the union (obesity, smoking etc) or Millennials being the just as Republican as their parents to the tune where they won't even drop 10% in Republican voting.
This is great analysis although it brings up the question of if the black vote can also become slightly depolarized in 10-20 years in Mississippi. This seems crazy today but so did the notion that Trump would match/slightly exceed Romney’s performance with Latinos in early-mid 2016.
A slightly more friendlier face GOP that still has a staunch center-right position on immigration, pro fair trade, and pro manufacturing could end up doing 5-10 points better with the black vote in Mississippi down the line. This is a state with a lot of black manufacturing workers after all. We do know young black men are already less democratic than their elder counterparts.