As confident as I can be on the basis that I'm relying on the expert opinion of others.
An article I was recently reading was all about how flameproof Trump is. He has a base that will pretty much vote for him no matter what he says or does - that means that anyone attacking him can only lose votes, not gain them. For that reason, nobody is attacking him properly from within the Republican party. That will change when it's down to two candidates.
By this point, pretty much anyone who is going to vote for someone like Trump is already going to - there's very little Trump can do to win new voters amongst Republicans. So as other candidates drop out, their votes should (obviously just theory) go anywhere but to Trump. The only thing that will stop that is stubborn candidates refusing to drop out early, but there's at least one that drops due to having no hope and another will probably take a deal from the other "not Trump" candidate.
Of course, that all goes out the window if there's another attack from Muslamic Infidels. In that case, I'd expect him to walk a win - possibly into the White House.