It was an unusual fracture from a direct blow rather than along the usual lines of stress/failure but unless there is vascular compromise I see no reason it won’t completely heal given time, something he did not give it initially. There is no reason for him to return early now, except for a few wins of which he will have a more than adequate sufficiency when he does retire, or to prove something to the opposition which is how he sustained his humeral fracture and a previous significant shoulder problem. Maybe he will be able to improve his shoulder, which at this point in time I see as the factor most likely to limit his career. With the one lap pace his brother (EDIT to be more accurate mainly Nakagami before the most recent race) has shown i don’t think we would have seen him having any 10th place finishes due to intrinsic lack of pace, and if this year’s Michelins are problematic he is the guy who can ride around such issues par excellence.
Nevertheless whoever wins this year is a worthy title winner, he is not out there as a result of his own riding error and lack of judgement.