I think Canelo will fight smarter in the rematch. He'll come better prepared, too. Bivol will come in more confident and that will probably translate into a willingness to press more and up his aggression. That might not be to his advantage since he'll be more open to counters. Bivol is good at picking his spots though, and limiting countering opportunities in general, but every fight is different.
You're right in that Canelo does have to fix his stamina in the rematch. Fortunately for him a fair bit of that was down to him putting everything into those big swings that constantly missed or were blocked. If he avoids falling into that same type of pattern and is mindful of it he won't drain himself and tire as quickly. Improving his cardio, pacing himself a lot more intelligently, and just being more efficient when throwing his punches should help him a lot. Energy conservation will be important. Staying behind the jab and incorporating more feints would also help since it takes a lot less energy than constantly throwing nothing but heavy power punches like Canelo did last time out. I'd pick Bivol to win the rematch but Canelo does have a shot at winning if he makes the right adjustments and there are a few of them he'll have to make to get the W.
