It seems as if people have more natural endurance when they are younger but I could be wrong. Through experience when i was younger I remember doing jog a thons at my middle school. I used to to max out the amount of laps easily when I was 9- 10 years old. But when I got a bit older I found that it felt harder and I didn't even max the laps out. This was all before I even got into distance running.
Will he burn out? I doubt “burning out” would happen. To me it would seem pretty hard to burn out. You are more likely to get injured before you “burn out”.
Will he have a successful future? No one really knows for sure. All a runner can do is stay motivated, love running, and train consistently/correctly/carefully and see where he or she can go with it. We can't all be all-stars or Olympians however improvements in running can be a lifelong fulfilling thing.