Read my lips: There's no way in hell that Trump will release his tax returns, even when it becomes readily apparent and unequivocal that he's going to lose the general election in a big way. Why? Several reasons: (a) because he has a business reputation/brand name (whatever that means) to protect even after his loss, and (b) because he's not in the habit of saying "I was wrong." Interestingly, a good portion of Trump's business income comes from the licensing of the name "Trump"--so imagine how a questionable tax return could ruin that revenue stream. See, for example, https://www.washingtonpost.com/politics/how-donald-trump-can-make-money-even-when-trump-branded-properties-fail/2015/07/23/1ff64854-2ef1-11e5-8353-1215475949f4_story.html.