RE Trumpism doesn't end with Trump...
The sentiment in America which leads to so much support for Trump will remain, post Trump, that is obvious. But what is not so obvious is that Trump is extremely charismatic to those inclined to his views, and absent Trump, so-called Trumpism may experience a large decline .
In 2028 some Republican not named "Donald Trump" (at least I hope so) will have to oppose the Democratic nominee. And whomever that Republican is, it's very likely that he or she will have less appeal, perhaps far less appeal, than Trump to the average Republican voter.