Even if/when Hayward comes back healthy, I think it's time to think about using his salary+talent as a trade piece. The Celtics are confident now that they'll have Brown/Tatum/Smart for a long time, plus Grant and Semi providing competent-ish big wing depth.
If Hayward comes back off this foot thing and looks good (as he did after his return from the hand), there are teams desperate for what he brings who will give assets for him. Ideally you roll him into salaries that provide that long-needed trade ballast, while also adding premium picks and maybe solving the big body problem.
His salary+talent opens up so many trade possibilities that it's impossible to list them all here.
Again, this isn't a comment on Hayward being bad, and more that they're committed to a lot of money at his position, and he fits really well for Western Conference teams who need a big playmaking wing right now.