*Rubbing my crystal ball*
Mayweather will toy with him for a bit to make the crowd think that it's actually a match..and then he'll tear him apart. Connor will then make excuses for the loss and will try everything in his power to get Mayweather to step into the cage with UFC rules. If Mayweather is smart he will stay away from an MMA bout, but we'll see just how much the wallet can coerce him.
I'm pretty sure Mayweather loses in the first round of an MMA rules fight against McGregor.