Mayweather WILL retire undefeated. As much as many want to see him lose, there's nobody in the sport right now that can beat him. It's wishful thinking, but he's a total master in the ring. Forget about the boxing skills, he simply outsmarts other fighters...That's where he really beats you. These opponents look great against other fighters, then they get in the ring with Floyd and then you're like, "WTF?!"...always happens! NEVER pay attention to a previous fight when their next open is Mayweather. Throw that out the window!
Mayweather will not retire undefeated. While he is the best fighter today, he loves the money and the limelight. So much so he will keep fighting when he should call it a day. Eventually he will end up losing to a fighter younger or bigger (or both). Father time catches up to all fighters, and Floyd won't be the exception.