Do I think Pac will beat Mayweather. Probably not, BUT I think Pac has a better chance than anyone.
Like Marquez said in the post fight interview, Pac is a totally different type of fighter.
Marquez is a thinking fighter, a technically savvy fighter, a very orthodox fighter. He stands in front of his opponent rather stationary.
Marquez = great technician.
Pac is southpaw, who darts in and out quickly, firing a bunch of punches from various unusual angles. He is very fast, especially compared to a Marquez who is not getting younger.
Pacquaio = is a buzzsaw.
Styles make fights and I think Floyd will have to adjust his defense as he won't be facing wide left hooks. He'll have to deal with Pac's right hook coming from odd angles mixed with a pretty devastating left hand. And unlike Marquez, who I think could have landed several of his best punches and not have the zap to hurt Floyd, I think Pac CAN hurt Floyd.
Marquez was made to order for Floyd; he's older, clearly slower, could't hurt Floyd with his punches even if he did land them, and is very orthodox. Made to order for Floyd, and the outcome of this fight was really obvious and 100% what I expected when the fight was first announced.
Pac is much quicker, most importantly more unorthodox, and has more power.
I'll say right now I'd say it's 60% Floyd 40% Pac. Mayweather is favorite, but Pac an extremely live underdog.