I agree with the other posters that supposing no school will work for a 3 year-old is pretty suspect. I have seen so many posts like this over the years and I think generally, testers and psychologists do a serious disservice by making such claims for much older kids, let alone 3 yo. I had such advice given to me and it freaked me out and as I learned way more about PG kids, I came to recognize that it was quite short-sighted.
I like jack'smom response about structure. Pretty much the point of early education is teaching children to follow rules and make transitions between what they want to do and what needs to be done next and learning to interact in groups. 3 yo are not usually good at such things and part of growing up is mastering enough self-control to interact well with others. These are things anyone needs to learn eventually to function in the real world unless they have some very, very unusual situation where everyone caters to their every desire. I don't know anyone like that. A more structured situation may actually work better and your son may adapt as necessary.
In large gatherings of PG parents, I've seen an astonishing array of choices made and educational situations from college at super early ages to lock-step education in a regular classroom have worked wonderfully for very, very smart kids. I don't think IQ precludes any particular educational option and the interaction of IQ, available options, personality, teacher, other activities, etc., matter a great deal. Some PG kids can daydream and create poetry in their heads while bored in a regular school and some go nuts. Some kids find great outlets for their energy and talent that aren't related to school and school becomes secondary to high level sports training or music or whatever. Some PG kids get along great with their age peers and some prefer other ages depending on emotional maturity. Some local areas have great school options for really smart kids and some areas have nothing worthwhile. It's pretty hard to predict those things for a 3 yo and seeing how things unfold over time might be more useful than scary predictions made by someone who met a kid for an hour.
