I don't believe there will be more than 60 quests, there are special mission however, if you wish to pursue those.
I'm pretty sure there are 51 quests in the game. when you beat the 51st you get power-up data that takes 1 more damage off every kind of attack, making the total amount of damge taken off 7.
Please don't calll me lyer! the first time I caught Regigigas(at Styler Lv.63), I got a 1-line capture! o_0
Oh, and I have beaten all the special missions. now I'm gonna transfer Darkrai, Riolu, and MAnaphy egg to myDiamond! yay!