I've been around a few decades (over five) and spent a substantial amount of that time dealing with those in society that don't get their coffee at Starbucks and can make you disappear.
So, with that in mind, let's look at our current President, who's legacy is now cast in stone.
Will he be considered great?
No. Nothing he has done is great. What has happened was by subterfuge.
Will he be considered brave?
No. He never explained his ideas with his belly against the bar. He lied, continued to lie and hides his lies with more lies.
Will he be considered a statesman?
No. To be a statesman, the citizens you represent, and foreign leaders you encounter, must find you exceptional, and respect you as a majority. That's not what we find, or will find.
Will he be remembered as a leader?
No. Being a leader means taking full responsibility for your actions, and those that are under your responsibility. If those you lead fail in their task, operate outside the law, or tarnish their office with malfeasance, there is no option, other than removing them from their position and demanding authorities prosecute; if necessary. Allowing those that broke the law to plead the fifth is not leadership, unless the leader is leading criminals.
Jimmy Carter wasn't a good President. His ideas clashed, he was perceived as weak, and the world treated the United States with disrespect due to his actions.
President Obama is worse. Not only has he surpassed Carter with his actions, he's lied, allowed his subordinates to violate the Constitution and ignores the laws he swore to uphold. World leaders shun him, if they don't treat him with derision.
Time will reveal more than is obvious. Obama's legacy will be of a bad President, a criminal politician and failure as a world leader. It's unavoidable and nothing he does will change his legacy.