I agree a little bit, but I think they will stay on board. I believe Trump can keep his folks happy and appease the moderates. (the Trumpsters like him, it’s personal; like the Obama thing) The toughest sell will be the “real” conservatives, the Cruz folks, social and/or economic conservatives. I believe that these people are sick with grief, rage right now, but that the thought of Clinton in the White House will draw them out of their stupor in the next 1-3 months.
I have a feeling Trump can actually win the election. Winning is something the GOP has not done for awhile. He could be a fairly decent President - we need to keep an eye on his choices for his administration in the coming months. But picking Kasich is a good start; I am not saying Kasich will go for it. And, of course, I could be wrong with all this. But if good GOP people get on board, Trump will hear them out, let them do their thing, He will just manage. That is where he is coming from. It will be like the Apprentice.