This will mean Democrats will have control of redistricting in 2021, correct?
It means that if state government is deadlocked in 2021, the court will be more likely to draw a Democratic-favorable map, though since they are a court they will not be able to openly gerrymander. Both legislative houses in PA are probably safe for the GOP for the rest of the decade, so it'll probably come down to the 2018 gubernatorial election. If the Republicans can knock off Tom Wolf, we'll be able to draw the Pennsylvania maps for a third decade in a row, which would be pleasant.