If in 3 1/2 years he is still able to muster an attempt at a campaign, I think some shit will go down - either the BMDs won't fund him at all, or the primaries will be far tougher than they were, or we could see a third party run.
And I do think a lot of Republicans will bail on someone that they don't believe can help them win. Losing is a sin, and losing to Sleepy Joe and Bi-racial Kamala will do it for them. Toss in that a fuckload of conservative Republicans are publicly supporting Harris/voting against Dotard as well.
And in addition to the BMDs, there's a whole shitload of Republican politicians right now who are not going to be patient enough to wait until 2032 if he thinks he can run in 2028, because they aren't going to want to see what new crop of up-and-coming Republican politicians will be fighting them in the primaries in 7 years.
And given how PACs work, we could easily see some of the BMDs telling Haley or somebody else to run against Trump and they'll fund her as a third-party, in an attempt to break Trump's hold on the party. All it takes is the threat of peeling off 5-10% of the GOP and MAGA is neutered in terms of Trump winning. Republican BMDs do not want to wander in the wilderness for 12 years. Shit, some of those fuckers are as old or older than Trump.