I don’t think the impeachment attempt will be successful. This is the same state rep who brought up impeachment before, and he didn’t get much support from the rest of the PA GOP. He still seems to be acting mostly alone.
Keep in mind that the new map changes the congressional districts, not the state districts. I seriously doubt that PA state representatives would personally take on such huge political risk merely in order to improve the prospects of fellow politicians in DC. They aren’t exactly altruistic.
Especially because even if all five justices go, it’s quite possible that nothing would change. The two dissents mostly agreed that the current map was bad, but wanted to avoid disrupting the 2018 election.
So the whole impeachment effort would be for naught if just one of them realized that reverting the map back in July would be even more disruptive. Plus, it’s quite possible for at least one of them to be annoyed by a legislature that thinks it can threaten a Supreme Court justice with impeachment.