If ever both party agreed for a rematch, I wonder which weight Division are they fighting, would it be Canelo's division? or Bivol's division? If ever Canelo go up in weight division just to fight Bivols in his natural Division, I think we will be seeing the same result like their first fight.
I don't think that Bivol can go and fight at 168 lbs, he has been a true light heavy weight fighter in his career. So most likely if Canelo insisted at this comfortable weight, Bivol is not going to take the fight. Canelo has 2 fights already in light heavy weight so I guess there is no problem for him moving up again and rematch Bivol. Although the result might still be the same as you have said.
Aside from that, Canelo don't have any power now to insist or demand what he want like to settle and contest their rematch in 168 pounds because he is now chasing Bivol, not the other way around. Furthermore, their first encounter happened in Bivol's division, so it's still better to make it happen in light-heavyweight and just like you guys said, this isn't the first time for Canelo.
Well, let's say that their rematch will indeed happen in 168 lbs. and let's say that Bivol have also agreed to it. The question is, is Canelo Alvarez ready to risk his belts and the undisputed title? I don't think Canelo have the guts to risk his status now because he already know Bivol's capabilities. Remember that supermiddle and lightheavy have only 7 lbs. or 3 mere kilograms of difference. Bivol will surely take that challenge for sure if that's the case, no doubt.