I think Trump will win and his supporters will get disillusioned with his work, because he won't accomplish anything. If he does lose in a landslide, then his supporters will eventually disappear and find the next person to cheer for. They might be able to blow the rigged election horn for a couple of days but they'll eventually get bored.
Many politicians have promised not to go away quietly. The supporters of these politicians have tried to say the same. Al Gore is one example. He tried not to go away quietly, and stay relevant, and it didn't happen. He's practically unheard of now. Just like Gore, Trump and his supporters will eventually fade after the election if Trump loses in a landslide.
No, I don't think that Trump is the type to lose with dignity. He is the type to make a load of inflammatory statements about why it wasn't his fault that he lost. Neither he nor his supporters are bothered about facts or subtleties, and like a good conspiracy theory.
No, Donald Trump and his supporters will not go away if he loses in a landslide because they will claim the election is rigged. They will say it is not fair for Clinton to win the White House, and they will make excuses. They will complain for the next four years.