While Tom Hardy lost the bet, he won recognition and praise, so maybe he was ok with it.
“Leo knows all” is actually a remembrance of the time Hardy was honored for his work.
If Hardy had the presence of mind to predict that The Revenant would finally be the film that won DiCaprio the elusive Best Actor Oscar, it’s possible that could have happened.
It’s not clear what exactly Leo’s side of the bet actually was if Hardy had been right, it might have been a tattoo of his own or something else entirely.