May's career is likely a wash.
He doesn't have much cartilage left in his knee. That's not something that's going to ever change.
He played too heavy for Roy's run & gun.
He's pretty talented, especially now that he's added a reliable jumper but he's never going to be able to play more than 40 games a season.
It's also a stretch to think that he'll ever be able to slim down since he's pretty limited when it comes to doing cardio.
I wouldn't extend him under really any circumstance