It's all a guess, we have no real way of knowing. But I'd think it all depends on what happens in the ring leading up to the KO. If something like what happened to Cotto or Hatton, then he'll probably go into some sort of depression, but knowing the Mayweather's reactions to everything, they see things a little different than the rest of the world so he may have some abstract way of absorbing the loss. If it's something like what happened to Pacquiao in the Marquez fight, e.g. just gets caught with one, then unless he turns completely mental, he should be able to bounce back.

I've been wondering with so many huge bets on Mayweather if they is any sort of watch on the judges to be selected from fixing the fight on the judges side. I also have to wonder if the Vegas insiders for the Bradley / Pacquiao fight knew something was up and why they gave peoples money back. One can easily see a couple of hundred thousand pooled moneys, to secure bets, could go to a judge's secret account. That kind of temptation would be hard for anyone to not score close rounds in a specific direction.