Pac vs Mayweather will be an entirely different fight. Pac's superstar status will force Mayweather to weigh in at a disadvantaged weight and won't just be a few hundred grand compensation if he goes over like he did with Marquez. If Mayweather weighs in more than he should, I'm sure the fight will not go ahead.
I don't think Pac has much superstar status to be honest. His PPV ratings are really quite poor. Of course this isn't helped by the Philippines not having PPV.
Neither Mayweather or Pac are huge draws and both rely heavily on their opponent bringing in the fans. If Cotto v PacMan is on PPV it will bomb.
Both are too greedy and I can't see the fight going ahead. I think Pac needs Mayweather more than Mayweather needs him. He seems to be looking for the big name fighters whereas Mayweather was more than happy fighting less of the big names.