While he has maintained a substantial lead now for months he has never cracked 30% in the polls, at least that I've seen. Meanwhile, Hillary is over 50% in many polls. If Hillary gets the nomination most Bernie supporters like me will happily vote for Hillary over any GOP candidate, few will stay home. With the vote so spread out in the Republican Party I'm not so sure that establishment types and evangelicals will find Trump palatable and may loose enthusiasm and stay home.
.....and, if I may, let me add a few other factors into the hodgepodge of this primary and next year's election....
First, Trump is much more "liberal" than he is that strange definition use by right wingers, "a true conservative".
Second, Trump has actually benefited by the unprecedented large number of candidates, and even with a few gone, the number is still substantial.
Third, there is a considerable number of senate seats that will have to be defended by the RNC......and I have no doubt, that democrats will go all out to bring out the vote next November which will greatly help Hillary.
Fourth, another incentive to get the vote out, is the very likely scenario that the next president will be nominating 2-4 court Justices....
Finally, this primary has shown that Hispanics and Latinos will certainly show up at the voting booths since they are really pissed at republicans.