Jack Sock is generally considered the #1 American recruit, but he's undecided on if he'll play in college. I think if any incoming player is going to shoot to the top of the rankings, it'll be him. Giron has an impressive resume, it'll be interesting to see how he fares. Don't be deluded by some of the stuff you hear on other message boards, college tennis is a step up from juniors, not a step sideways.
Vinsant and Fratangelo are classified as juniors. They've got another year before making the college decision.