Interesting discussion here!
My son also just finished second grade, and is the youngest (or nearly) in his class with an August birthday. He's more than keeping up, both academically and socially, so far (though who's to say what middle school will bring.) We have no plans for him to skip grades- he's already young for his grade, the kids in his class seem to be a particularly friendly bunch, and he loves sports (so jumping ahead MORE would more or less remove the option of school sports from him.) But more than that, anecdotally, the kids I knew who skipped a grade were no happier than ones who didn't. In fact, they were more troubled in general, and had trouble in middle school and high school keeping up from a maturity standpoint.
So yeah, my son is bored with school. Luckily there's a GT program- they only meet once a week but he LOVES it. And starting in 6th grade, there is the option in our district to go to a GT magnet program for middle school. The GT kids are automatically accepted, so it's just a choice- go to the excellent zoned-to middle school with some GT-specific classes, or choose the GT magnet program. That program is a subset of a regular (excellent) middle school, so the kids could still do band, sports, etc with the rest of the school.
We will let him decide whether to go the intensive-academics route or the more traditional route- I'm glad we still have a couple more years before that decision is before us.
In the meantime- we're using this summer break to do all sorts of fun stuff- since we both work full-time still, he needs daycare in the summers. But around here there are a lot of options. He's already been to a soccer camp, a python-programming camp (morning) and "digital playground" (afternoon) where they learn to make websites at the local state college, a general run-around-and-play-sports camp, and this past week at the local nature preserve (canoeing, fishing, making pots out of clay dug out of the ground, hiking, generally getting muddy). Awesome. He still has baseball, sailing, gymnastics in front of him. I love that he has summer vacation to take a break from the classroom and do different things.
We're also reading Tolkien together- he's halfway through The Two Towers and loving it. As a verified lord-of-the-rings geek, I am utterly charmed by his enthusiasm :)
I had the option to go to a university program for my last two years of high school- I'd have lived in the dorm with other students in this program, and simultaneously done the first two years of college with the last two years of high school. I very nearly made the decision to go. But-- I loved band and didn't want to miss out on the typical high school stuff. In the end, either might have been a good decision, but I'm glad I chose what I did. It worked out very well for me. I ended up with a BS, two MSes, and a PhD though 13 years of college/grad school, so I'm not sure accelerating that would have mattered much :) I guess I love school.
In any case, if I were you, I'd focus on enrichment through elementary and middle school, but staying with his peers in the same grade. And then look at options for the last years of HS if he's interested in accelerating things.