Maybe. But if he wins definitely not as GGG would be "officially" 1-1-1 against Alvarez and if GGG wins a war then then they might go for round 4
I think he retires, win or lose. He’s already semi-retired and I hope he calls it quits. GGG has slowed down a lot over recent years. I’m a fan and don’t want to see him take too much punishment or get beaten by a much lesser opponent. He’s getting close to that territory and it’s too common in boxing. Look at RJJ, punch drunk and a shell of his former self. GGG made a lot of money and doesn’t need to keep fighting. Father Time has the best record in boxing.
If he gets stopped that'll be his last fight, 100% sure. Losing on points, especially if he's not outclassed, still opens a window for a couple of fights in 2023. And GGG won't be retiring if he somehow ends up winning, take that for granted. He'll go on and defend those belts in 2023.
It all depends on how he loses? If he is stopped with a bodypunch he might retire, but if he loses in a controversial decision, and any decision will be controversial in boxing, he will keep boxing and want a 4th fight.