Trump would be gone. But his supporters would probably think Trump lost because he wasn't extreme enough. They would support another Trump-like candidate if one shows up, and the whole thing starts all over again, except with even more extreme rhetoric.
I disagree, Unlike Cruz or Goldwater before him, Trumps support is based around a cult of personality rather than policy or ideaology. This is why many in the establishment including preibus seem ok with nominating him and losing because not only does it position a more moderate candidate for 2020 but also many of trumps supporters, without their God to lead them, will continue their normal voting patterns