Assuming Canelo needs something else for his legacy, I reckon he battles the winner of Beterbiev versus Bivol. That will bring him prestige particularly assuming he wins and becomes undisputed in two weight classes like Crawford and Inoue.
That's the best thing for him to do to gain more popularity, but that means climbing up again in weight, which he failed against Bivol. If Beterbiev wins here via KO, that means he is too much for Bivol, and I don't know if it's wise for Canelo to challenge the boxer that defeated the boxer who defeated him.
Canelo has never been KO'd in his career as a boxer, and maybe that will be the time that he'll suffer his worst defeat at the hands of Beterbiev, who is a 100% KO artist. I'm not sure he is up for that challenge as his legacy is also at stake big time.
He can still chase for greatness still by fighting Benavidez or going after a rematch with Bivol to avenge his defeat. But so far none of that has happened, he chooses to fight the twins. Years ago he had plans to even moved to CW and fight the WBC champion for a catchweight?
What happen to that plan? Now, he is fighting at 154 lbs and 160 lbs boxers? He used to go up in weight and challenges those champions. But it seems right now it's the other way around for Canelo, asking boxers if they want to fight him to go up to his SMW. But doesn't want to fight the likes of Benavidez or even Munguia because he thinks they didn't deserved the fight or they are "Mexicans".