if Alvarez ultimately turns out to be nothing special? I'm not sold on him yet. We can all agree that this is the biggest fight currently.
He's finally after so many years fights the opponent the fans want him to fight and before he's on the slide or already lost to others. It would be bad for his legacy if he didn't fight Canelo now, otherwise it would just add up to the ones he didn't fight. So it doesn't matter if Canelo turns out to be a dud afterwards, because we don't know that now.
It only helps his legacy now. If Canelo goes on to great things in his career it will look even better. Based on now Canelo is listed as the Ring Belt holder. Floyd would hold 2 Ring belts in 2 different weight classes.