Short of him dying (which is always possible...election is a year away), he will be the nominee. Or if he drops out of his own volition (which he shows no signs of doing). He will be the nominee. That's a given.

Trump almost certainly will be the Republican nominee, based on the polls I've seen. Unless some key states refuse to put him on their primary ballots (I think a few are trying to make that happen because of his legal problems, past and present). Which may or may not be Constitutional. I dunno.

I predict Trump v Biden next year. In which case Trump will scare enough people to show up to the polls to vote against him, just like last time.

But if Biden expires? That would be interesting. As VP, Harris is the likely successor. That would be very interesting, and a bit scary (because that would not be a slam-dunk).