Well, sure, if the justices wanted to, they could get rid of population-based apportionment of state legislative districts. It would be a dumb thing to do, but this is a court inured to the practice of doing dumb things.
The case in question is Evenwel v. Abbott – the plaintiff argues that Texas should not base state redistricting on the distribution of its population, but rather on the distribution of its voters. The motivation for the case is to strip power from urban areas in favor of the rural conservatives.
Central to the conservative argument is that apportionment of representation by population size “dilutes” the power afforded to voters by distributing representation based on both the voting population and all the other people (kids, foreigners, prisoners, non-voters) who happen to live in a state House or Senate district.
In other words, the plaintiff believes that government representatives do not serve all the people in their district. The plaintiff believes that government representatives serve only the people who vote, and everyone else can suck eggs.
Not surprisingly, every court that has heard the plaintiff’s argument has rejected it out of hand. Surprisingly, the U.S. Supreme Court didn’t just reject the argument out of hand, which has everyone worried. Needless to say, a decision favorable to the plaintiff would be devastating to the efforts of underrepresented minority populations to redress the inequalities they face.