If George Soros announced today that he'll donate $5 million to charity if Mitt Romney released all his tax returns for the past 10 years, would you expect Romney to do it? And if he doesn't, do you expect people would wonder why he refuses to help charity and what is he hiding?
This is a stupid stunt that will result in nothing except some brief publicity for Trump, and will have zero impact on the election.
Is this wishful thinking on your part? Obama released his "birth certificate" as a result of Trump's questions.
President Obama, love him or hate him, you do not know him.