Our story is sort of like kickball's, except we SB-v'ed at 4.1. I was thinking DS should go to kindy early (at 4.8, which he is now), and we needed the info in the spring to get the ball rolling. When we found out he was HG+ and it was recommended to us to let DS play another year, we did so.
And it is amazing how much things change in a year. Last year, through the end of 3-4 YO preschool, DS was extremely clingy and didn't want to leave me and had elaborate goodbyes and rituals. Today, I dropped him off, and he happily said his goodbyes and went off to play. We have him in a play-based 3x/week afternoon preschool.
Re: worries. I have to mention that I did worry a lot about how DS was going to manage in school - i was certain he needed early entrance to kindy. But I told DH I would go along with the tester's recs, and I'm happy I did. First, my worries have gone mostly away - i know what I'm dealing with, and i'll be prepared when the time comes for "real" school. Second, with another year of no school, easy to put off any residual worries I might have wanted to have.

Third, my wiggly kid doesn't like to sit still for long periods of time, and he acts his age quite a bit, and he would have been a trouble maker. Other things have changed though. For instance, he is now reading at an incredibly high level (with intonation and everything!), so i'm thinking we have to rethink our plans of kindergarten on time, then skip first; and switch it to skip kindy. But we'll have to wait and see. But I emphasize what a huge relief it was to know what we were dealing with in terms of our kid's LOG. It turned out especially helpful, since we underestimated what it was.
As for schools, the psychologist, who is a specialist with HG kids, said not to worry too much until middle school, but expect to go through many different school options, including homeschooling. We live in a pretty small city (16,000 population), with few choices, so at first we were worried. But now we know homeschooling is an option, and we are brave.