Pac is the P4P champ, Floyd isn't. Pac has an ABC title at WW, Floyd doesn't. Pac is the bigger draw internationally, but will most likely outdo Floyd's PPV numbers (and definitely his ticket sales). It's Floyd who should call Pac out.
I don't think the #1 fighter is supposed to be doing the calling out. Let Floyd call him out. He's the one that came out of retirement to reclaim his throne from Manny. And he's already made it clear he ain't fighting Mosley. Who else is he gonna fight?