of course it needs to happen, but if only one side is willing to fight or floyd is in jail or whatever, life goes on, pacquiao will fight on.
Personally I think the winner of Bradley/Alexander would be a great fight for pac. For one, it would be nice to see pacquiao fight guys his own size again and they are both undefeated, young and in their primes. They would both give pacquiao some problems. They are fast and slick enough to be good tests and good preparation if the Floyd fight ever happens too. The only downside is neither are big names, but I'm sure it could still sell 750,000 PPV's.