Nothing is confirmed, but my SOURCES tell me this is what will probably happen.
Pacquiao as of right now is refusing to fight Cotto at a weight above 150 pounds and that is causing a domino effect, which will have Cotto fighting Mayweather on May 5th (Mayweather has no problem with a catch weight of 150).
As far as Pacquiao, it doesn’t seem his team has any strong interests in fighting Juan Manuel Marquez again, not necessarily because they don’t think Pac can win, but they don’t want to pay JMM $10 million which is what he is asking for.
Without Cotto or JMM unavailable, Timothy Bradley would be the pick for June 9th.
No outdoor arena would be built, as the fight would probably be in the MGM.
While neither fight is even close to what a Mayweather vs. Pacquiao would do in terms of money and PPV, Mayweather vs. Cotto would crush Pacquiao vs. Bradley in terms of popularity and interest.
Cotto is the 3rd biggest draw in boxing in the US, so matching him with the 1a/1b biggest draw would be a financial windfall and the next best thing financially for Mayweather.
When we have more details, will let you know.