Yep, Mayweather is going to dance around and keep scoring points and not take any big chances. That's what he does. He knows there is no way a guy who has never boxed in his professional life is going to outbox him. McGregor's only chance is to catch him being overly aggressive and knock him out. Mayweather isn't going to let that happen.
I think he has a chance based purely on the absurdity of the fight. It isn't an MMA fight, but MMA striking is completely different to boxing, even MMA fighters with backgrounds in boxing don't fight like boxers do. Mayweather will be defending for the entire fight, but he's defending against a style that is totally different to what he's used to. MMA striking involves a lot of forward/backwards movements in relation to your opponent, rather than standing in range and creating angles to strike from.
This is very very very stupid. Personally I think it's going to be a shit fight and Mayweather will win on points. But MMA fighters have insane cardio and general fitness levels. MMA fights are shorter, but the rounds are long and the grappling is extremely tiring. He could easily find himself outpaced if he isn't prepared.