Yes, a lot of them become legitimate 7.0s who make a good living playing tennis on the tour. So perhaps would we rate this junior as a 5.5-6.0?
I honestly don't really know the difference between a 5.5 and a 6.0. I've watched later to be successful Division 1 players at the high school level. Some of them played ugly but their later rankings suggest they were legitimate 5.5s. This kid is hitting a lot cleaner than those guys, but I still haven't seen him in match play. I'd provisionally rate him 6.0.