There is literally zero chance Hayward opts out of this 34 million dollar deal, mainly because no one is going to offer him another max deal or a hefty long term deal.
Take the money, prove your healthy, cash in on a long term deal next year.
But that's just it. If the Celtics offered him a 4 year, 20 million dollar a year deal if he opted out, he might consider it. If he opted in, he would be betting that he'd be able to get at least 46 million in the three years following this year's contract, or roughly 15 million a year. He might get that. I think that's roughly what he is worth for the Celtics because of their roster construction. But he might feel like he is worth more--indeed, he probably could get a bigger contract from a lottery team wanting to get into the playoffs.
But there is another complication. The salary cap will adjust with Covid from this year, and there will be a ton of free agents available in the summer 2021, which means he would have competition for his next contract. He could find himself with nothing more than an MLE, especially if he has ankle problems this year. In that case, by opting in to his 34 million dollars, and getting a 3 year MLE, he would have lost roughly 15 million dollars compared to the 4 year, 20 million dollar a year extension that the Cs might offer him this off-season.
Opting in, but only getting an MLE next off-season because of competition: 2021, 34 million, 2022 10m, 2023 10m, 2024 10m for a total of 64 million over 4 years.
Opting out and resigning with Cs for 4 years 20 million would give him 80 million over the next four years.