Will Mayweather fight the winner of Cotto-Pacquaio, or does he just want Pacquiao?

All in the title really. I'm not convinced that Mayweather will fight Cotto if Cotto manages to beat Pacquaio. I don't see the financial incentive that Pacquiao brings in a Cotto fight and I don't see the size difference that Mayweather seems to love so much. If Arum really wants the potential megafight that is Pacquiao-Mayweather, he should have never taken the risk with a Pacquiao-Cotto fight. Now don't get me wrong, I am pumped up for Pacquiao-Cotto, which is a 50/50 fight in my opinion, but I think boxing needs a megafight and I think we might not get it. Thoughts?