Predicting what Trump will do post-loss probably ought to be based on past behaviors. And for a very telling look at that, one ought to watch this incredible piece by Maddow interviewing Garry Trudea, who has been covering Trump for a long while. Trump, you'll see, is consistent in his behavior and in his rhetorical moves:
http://on.msnbc.com/2aEBoJp
Jespah gets the tone/behavior quite well. And Robert's take is close to mine. The Palin precedent demonstrates how the scam can be run and Trump is way better at it than she was.
I can't see how he gets out of the debates. I doubt he wants to get out of them. He'll be center stage in a manner he dreams of and, apparently, needs as a function of his unique pathology. He'll interrupt, bully, be "politically incorrect", evade, boast, slander and lie. None of that is a problem for him. It's his mode of operation.
I can't see how he quits (and unless he does, the dudes on the right can't get rid of him). What he wants to avoid (however consciously or not) is ego-damage and brand-damage. Quitting would set him up too clearly as being subjugated - by a woman. So he'll run and lose.
And that's when the shitstorm hits. How ugly he behaves is definitely a question. Voter fraud, rigged election, unfair press, GOP trying to tear him down, lazy voters, proof that America is a dung-heap and heading for worse - all that and more will be spit out. "America could have been great! It could have been amazing! Millions voted for me. There's never been anything like it! But you proud, patriotic Americans who voted for me - and I love you! I really do! - got shafted. Don't take it lying down. Reject this corrupt system before its too late. Maybe its already too late. I fear it is".
He'll maintain a following just as Palin did for years. And he'll scam them for every penny he can get, as Palin did and as he's always done. He won't drop out of sight.