With Part III demonstrating how Mitch McConnell got exactly what he wanted by forcing Reid to use the nuclear option, we now have enough to say what happens, basically, with Scalia's Supreme Court seat, and judicial filibusters more generally.
The filibuster is either non-existent at the Supreme Court level, or just an illusion. Remember from Part I that in 2005, the Democrats caved on the filibuster because of the threat of the nuclear option. Democrats got basically nothing from the deal, but they caved anyway based on the abstract promise of some possibility of maybe being able to filibuster in the future. Maybe.
If Republicans can peel off enough cowardly Democrats to reach 60 votes, they don't need to invoke the nuclear option to confirm a Trump Supreme Court nominee, but if so, then the filibuster exists only as an illusion because it cannot be used in practice by Democrats. Were positions reversed, though, Republicans would certainly filibuster, and Democrats would be forced to go nuclear, as they did with the Third Circuit under Obama with Reid.
Alternatively, suppose Democrats don't cave. They do filibuster. Republicans can't give up the Supreme Court seat. The whole point of McConnell's gambit after Scalia's death was to hold the seat open for a Republican President. To let Democrats block it now would be to give up after victory. They would have to finish the job on the nuclear option for the courts and extend it to the Supreme Court.
So, either the Democrats cave and the filibuster is only an illusion for court nominations, or the Democrats don't cave, and the Republicans finish killing the filibuster on court nominations. Either way, there will be no functioning filibuster on court nominations.
Do you like that? Do you want pure majoritarianism? Remember that the Senate is not really majoritarian in its apportionment anyway. Did you like the filibuster before? Did that depend on who was in control? Of course it did. The filibuster was a procedural issue, and it is extraordinarily difficult for people to separate procedural preferences from their outcome preferences.
William Riker (yes, there really was a political scientist named "William Riker," and no, that's not why I majored in it) called this the "heritability" problem. Process determines outcome, so your preference over process is the same as your preference over outcome. Deal with it. Or don't. But functionally, the filibuster is dead on court nominations.