Depends on:
a) How dedicated he remains
b) How well his nutrition and sleep quality is the remainder of his high school career
c) If he is injury prone or not
The most talented distance runner I ever saw back in High School was the type of guy you would have expected to be a top contender at Footlocker Nationals--- but he never reached his potential because he was always injured. I kid you not, he was missing entire xc or track seasons interchangeably from his Freshman Year - Senior Year.
He never ran high mileage, coach was extra careful with him and tried to get him to bike or swim, doctor's were checking up on him for common problems like flat feet, and so forth. No idea why he was so injury prone.
From your guy's times, it would be a huge disappointment if he wasn't running sub 4:20 / 9:20 by his Senior Year, and that's a conservative estimate based on the mpw & times he has already ran.