They take it from Trump they are a dead party. They will lose everything and their little country club will only have a few ahole members..they will be completely 100% irrelevant.
Several problems there:
First, if Trump did leave and take his supporters with him, most of them are Trump supporters, not Republican supporters.
Second, the GOPestablishment doesn't care what the 'little people' think or want. The GOPe only care about maintaining their club, because that gives them access to power and money.
Third, the Battered Conservatives Syndrome will continue. Conservatives take a beating every presidential election cycle, and they still hang on to the Republican Party. They can't change it from within, because they have little power. They can't change it from the outside, because they have little power. But they hang on, vote for the GOP Selectee, and basically vote for the same and expect a different result.