Canelo's solid. He won a close decision over Austin Trout, who's no slouch. But he's more of a blue-collar slogger with mediocre hand speed and just ok footwork. So it wouldn't surprise me at all if Mayweather picked him. He chooses his opponents very carefully and basically never steps in with anyone who has a realistic chance of doing damage. He'd overwhelm Canelo with his hand speed and countering the way he does everyone else who's slower than him.
I'd love to see him take on Amir Khan, but doubt he will because Khan can match his hand speed and movement.
I respect Mayweather, obviously a great fighter. But he'll never be remembered as a P4P legend the way he hopes because of the way he's always sidestepped taking on the best while they're in their prime.