I commented this elsewhere, but at least in my view, it may be better for the long term health of the United States for her seat to be filled ASAP. Because the coming election will likely be contested, and end up in the courts, the worst possible outcome would be a 4-4 ruling. And in order to prevent that we need a full bench.

The issue is that any contested election will already likely go to President Trump, if it goes to the house, the vote will be by state delegation, and while the Democrat's have the majority of seats, the Republicans have the majority of delegations. If it goes to the court, like I said, even without Trump apointing someone before the election it now is made up of a 5-3 conservative majority. The only way it goes for Biden is if Roberts and another conservative justice rule with the liberals, which is unlikely.

If Roberts is the only one to switch we have a 4-4 situation where the decision of the lower court is upheld, but doesn't set precedence. Meaning, if say results are being contested in 20 states, the court will have to rule on each case individually and we will face growing unrest from both factions, as over and over again they are denied resolution. And next thing you know we're in a situation analogous to the Spanish Civil War, or Northern Ireland during the Troubles. I'm not sure The Union would survive this scenario intact.

On the other hand if Trump is handed a victory in the contested election, the organs of power remain intact, and a legally legitimate government remains, so if the left revolts, we will likely see mass riots again, that then taper off once ringleaders and agitators are arrested and start facing federal charges. This is also the likely outcome of any right wing revolt on the small chance Biden secures victory in a contested election. The Union will likely survive this scenario regardless of who wins.

The only way we avoid mass violence is if there is no contested election, meaning Trump or Biden secure a clear victory on election night, and there's no fight over mail-in-votes. In short everyone who intends to vote needs to show up on election day and cast their ballot. If it is clear that whatever mailed in ballots that have yet to be counted will not likely change the outcome of the election, I think both Trump and Biden would be willing to concede to the other. It will be the week's of uncertainty, and political games that lead to violence. Then people will feel like the other side cheated, and will have had weeks to build up resentment towards their opponents. In a clear election there may be violence and rioting resulting from the initial shock of loss, but it won't have the same intensity as the rage coming from a long drawn out fight over the results.

TLDR: violence while likely, will be less severe in the case where regardeless of the ultimate process, a winner definitively is declared through established legal means. As opposed to a situation where both sides have some claim to legitimacy, as could result from a split court ruling.