Mayweather already sais that he doesn't have to do it again what he had done better in their first match, I love to see both of them doing it again with both of them healthier and in great shape but it seems Mayweather doesn't have a motivation to come back again, because he believes he would get the same results.
Is that really the reason? I don't think that he's telling the truth. Anyway, they've earned enough with their match so if ever Mayweather runs out of money or does want to add more money to his bank account.
With just one ping to Manny, this match is possible. He's the one that just have to make an action to trigger the fight.