Not just gerrymandering, there's more to come. Trump is talking about issuing an executive order to outlaw mail voting and voting machines. No, he has no authority to do that, but as always, who's going to stop him? It's not unlikely R's in Congress will push through a bill for him to sign doing the same thing. That way while it's being fought in the courts, R's can just declare elections in blue states illegal and refuse to seat the winners. Except their winners, of course.
Disenfranchisement will of course proceed apace.
Note that none of this is just Trump's doing. The Republican Party has been trying to destroy democracy for several decades.