I’ve heard the possible resignation angle, but that doesn’t fit the bill of a serial narcissist. Certainly, if Mueller/The House get their hands on his taxes then as you say, there may be additional pressure. Trump however, has been a megalomaniac for quite some time. It’s not in his nature to walk away. Thus, I’ll enjoy watching him squirm for the remainder of his Presidency, which I do not see lasting past 2020.