Two of my kids have multiple skips between them. They've also attended small private schools. The small school environment helps a lot.
For my kids, skips weren't a big deal at young ages. The fact that your son's close friends are in the higher grade would make a full skip a lot easier --- maybe even easier than staying a grade down (I don't know, as I don't know your situation). If he's asking for the skip, I'd say that's a strong positive.
Skips can feel awkward later, for a while. This is because older kids generally enter adolescence ahead of the skipped student. This factor can get played down, but it's real. That said, it's less dramatic with a one-year skip, unless the child is small for age or socially awkward. If a single-grade-skipped student who makes friends easily is a little bit tall and/or enters adolescence slightly early, people might not even know about the skip unless s/he tells them.
A good resource is the
Iowa Acceleration Scale, which helps make an objective assessment about a grade skip.
I agree about not worrying about potential future skips. Worry about that problem if it comes up.
Overall, I advise that you think about what will work best for your son, while using objective information to help you. Some people are very pro-skip and will advise you to go ahead. Others have the opposite opinion and will foretell doom if you let your son skip. None of those people know your son the way you, your spouse/partner, and your son do. The challenge is to find a path to objectivity and make a decision that will work best for your son's individual situation.
