There's always a constant flow of coalition partners from one party to the other so if the Democrats snatch up all the Hispanics by selling out black interests, the Republicans can easily pick up on that old coalition partner.
It's the math of winning in single member districts that drives this rough balance ~ in general you need to get 50% of the vote plus 1 more vote ~ and if you don't you tend to lose. If you lose you've got nothing to give your coalition partners and some are feckless when it comes to political loyalty!
We will see how it plays out, but it seems to me that it simply does not matter if Republicans hold seats or even how many seats, because the government agenda always moves forward.