Personally, I believe that Trump is not going to honor the "pledge" he took not to run as a third party candidate when the RNC chooses not to have him as the Republican nominee.

Trump will say it was just his way to get around an "illegal contract" and will use it to show how he can undo any Presidential order he deems an "illegal contract" in his mind.

Thus being said, in short, Trump will run, will siphon off votes from Republicans, and the Democrat gets to be President - again!