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.