The reason this case is significant is because the rules around partisan redistricting could become stricter. Originally the decision was that Wisconsin’s redistricting plan was an impermissible partisan gerrymander. The State is claiming that the decision was a watered-down interpretation of the standard test.
If the Supreme Court upholds the decision, it could change how voting districts are created. When combined with the rules around race-based districting, it could become exceptionally difficult to draw legal districts. Alternatively, the Court has been given the option to say that the Court cannot consider political jurisdiction claims. Taking this option could mean the expansion of State power in drawing electoral districts.
Like most cases in front of the Supreme Court there is no good way to predict the outcome - especially before oral arguments are heard. However, the decision could be fractured with no real result, leading to an uncertainty in approaching the issue. Or a couple of weeks after the decision, we could see most if not all States face partisan gerrymandering challenges to their districts if the rule about partisan gerrymandering is made more rigorous. Oral Argument is October 3rd. It will be interesting to see how the nine Justices are leaning.