Here's the sh!tty (although unlikely) part ... what if one of them loses? Do you plug the winner against the other guy (i.e. Mayweather beats Mosley, Clottey beats Pacqiuao, do we get Mayweather vs. Clottey)? Or do we still get Mayweather vs. Pacqiuao with one of them coming off a loss? Either way the matchup has lost some luster. Or, if one of them loses, do they demand a rematch, as is so customary in this sport? That pushes this dream fight back even further, and even further still if it goes to a deciding third fight. Or what if one of them loses and a brand new challenger steps up to take on the one who won his bout? Again, pushed to the back burner indefinitely.
I don't think either of them will lose, but while it's great to see neither guy chose a slouch as their next opponent it also opens the door to the possibility of making this dream Mayweather vs. Pacquiao bout less realistic/desirable. Boxing needs both guys to win, then suck it up and get this fight done.
If one of them loses, I am 90% sure the fight will NEVER happen, ESPECIALLY if it is Pac that loses. Mayweather would not bother fighting Pacquiao if someone else beats him. If Pac loses and Mayweather wins, Mayweather would likely fight Clottey and beat him with ease. (he will then beat the man who beat "the man"- he will shout from the mountaintops that Pac was never on his level) Now if there is a rematch clause, it would surely be enforced in this scenario, leaving Pacquiao vs Clottey 2 and Floyd needing a new opponent. If Mayweather loses and Pac wins, Mayweather would likely invoke the rematch, creating Mayweather/Mosley 2 and Pac in search of a new opponent. If either loses their upcoming fight, we will likely never see the dream matchup. Hopefully they both take care of business and get the deal done. A September Pac/Floyd matchup would break PPV records.