I think the people saying that he'll drop out it looks like he's losing fundamentally misunderstand Trump. Dropping out would be admitting that he's lost. But by losing the nomination outright, he can save face by saying that it was rigged. Trump's ego would never let him accept that he's lost. He can never fail, he can only be failed.
Most likely you're correct... that said, if defeat looks likely, he may look for a way to pull out and avoid humiliation. I think he could just try to blame a conspiracy that forced him out and that "usually he would have won in a landslide."
Or just cite health or family issues
