Yes, your son shows a lot of potential. Though I would think if he ran 5:30 for 1600 he could go faster than 2:42 for the 800, and that 18:46 5K would definitely predict faster times in the 800 and the 1600 both. But he probably has no idea what he is doing! Did he enjoy it?
I coach youth as well as high school. You say he had "zero training" but does he do other sports, especially other sports with running, like soccer or basketball? Lots of my middle schoolers who try running do quite well with their soccer or basketball base. My own son ran 5:20 as an 8th grader off basketball training mostly. He is now much, much faster as an 11th grader, having given up basketball for full time running. Other kids I've had who were running similar times at that age are now very solid high school runners, running in the 4:20's for the 1600 as sophomores and juniors.
Keep it fun, just let him keep doing whatever it is he is doing to do this well. If he really wants to run track, keep it pretty low key. My middle schoolers train 3-5 days a week. I have a 5th grade boy, age 11, who has run 2:24 for the 800 and about the same as your son for 1600, and a few others who have run in the 2:30's and 2:40's at age 11 off of light training.