I actually think they would, even if he does remain relatively strong the rest of the way. They hate Cruz anyway. Let him be the sacrificial lamb. They'll lose this election and probably some seats in Congress but they'll get most of those back in the midterms. Then they do their best to make sure Hillary doesn't succeed (they've had 8 years of practice), and then make another run in 2020. By then it will be 12 years in a row of a Democrat president, and people will likely to want something different. I can't image a status quo candidate like Hillary is going to shake things up enough to quell the anger that's out there.
The other choice is Trump receiving the cheers at the Republican convention, getting whipped by Hillary during the debates, and months more of The Donald alienating everyone but (maybe) white males, which IMO will do far more lasting damage to the Republican brand. They will take this from him by hook or by crook, IMO.