I wonder how many will simply become "Trump Republicans" and follow some other leader when he's gone? Or will some simply pretend to wake up and have realized they had Trump Derangement Syndrome the whole time and are ready to come back to reality?

These people aren't temporarily insane, they have always been this way. The same hatred and stupidity have been prevalent in US dinnertable discussions for decades, but much less in the actual halls of power because we used to have more collective sense to not grant people like that authority over others in general. If the rest of American society regains its agency, the toxic %25 will just go back to corroding the country as they were before. They are secure in knowing they will not be treated in the way they would treat others if given the opportunity.

At least the second hypothesis relies on the assumption that there will be a return to some kind of normalcy.

Watching this from the other side of the ocean, I'm not convinced that it's the most likely outcome.

My guess is politics are so divisive and social media so effective that until something significant breaks/Trump succeeds in complete Putin-esque capture of the government that we will see the president flip parties every 4 years indefinitely. People will continue to vote for whoever the current leader of their "team" is no matter their actual politics or values or even how they were chosen as leader for that matter because the perceived cost of the other side winning is always greater.

As soon as Trump dies there will be an increasing avalanche of "always never-trumpers", until 40 years from now it will be almost impossible to find anyone who admits to having voted for him. I already have anecdotal experiences of having conversations with people (on tape) in early 2017 celebrating/defending their vote of Trump who now claim to have never voted for him and say that anything on video was just a joke or sarcasm.