It's easier for him to retire if he loses the fight because if he wins, it would open more opportunities for him to have big fights and that means a big payday for him, unless, he will think of his legacy and will retire with a pride, like what Mayweather and Marquez did. In the end, it still depends on the decision of GGG, he know his limit and he knows what he likes to achieve in life, so let's enjoy the trilogy as we have been asking for it.
If he will beat Canelo on this one, I am sure, he may not think of retiring yet. But who will be his next opponent other than Canelo again? So yes, this will be interesting how this match will pan out. But in this trilogy, I believe, Canelo will win. As he is coming from a loss, he has the motivation to train and prepare hard for this fight. This is to regain his status and popularity. I am thinking that bookies may slightly favor Canelo here. But let us see once bookies give their odds to this fight.
If GGG wins, then he should go back to 160 lbs, there are a lot of young ang upcoming fighters on that division. We have Charlo and then Lara and also Jaime Munguia. So a lot of options for GGG if he chooses to continue to fight.
As for Canelo, at 168 lbs, we've said that he has clean up this division already, and that's why he moved up in weight by defeated by Bivol. The only one name relevant for Canelo at Super Middle is David Benavidez.