I don't think he's 100% physically, no. Go back and watch footage from his 2017 pre-season with the Celtics and you'll see the subtle difference. This shouldn't be surprising, given that we have recent news reports of ankle soreness and that he's been managing the injury all year. I just think it's too easy to say "it's just mental". Managing pain and soreness is mental, I suppose, but it stems from a real physical injury and recovery.
I think next year he will be more or less his old self. Not sure he'll ever be 26-year-old GH ever again, but then again, no 29 or 30 year old is the same as his 26-year-old self, regardless of whether or not they sustain an injury. Here's hoping he can be even better, even if he's slightly less explosive.