The hardcore supporters will either stop voting out of despair that "the deep state has won" or scream about it until they die. The less fanatical ones will move on.
I'm most interested in what happens after Trump leaves office one way or another - the Trump presidency has a maximum time limit, after all. The GOP are basically stuck with the huge problem of who amongst their ranks can actually succeed Trump. The next guy who tries to follow up on Trump is likely not going to be remotely as charismatic or capable of dealing with a smarter Democratic candidate who has learned from the 2016 experience and doesn't have the baggage of Hillary Clinton. The GOP is also stuck with a hopelessly divided caucus that has resulted in rather limited congressional progress on partisan issues.
Everyone and their mother ran for the GOP primaries in 2016, once Trump is out it'll be that all over again except without Trump, and everyone else in the last race was shown to be hopelessly underwhelming in some fashion, and in the case of Ted Cruz, he's probably loathed even more by his own party after he refused to back Trump at the convention. Mike Pence, winning in his own right? Haha, good luck with that.
The GOP is fucked in either 2020 or 2024 once Trump leaves office, barring a miracle candidate, really.