We grade skipped DD from grade 2 into 3 but academically it should have been to grade 4. We tried lateral extension to supplement including a third language and piano which were both pull out and ballet and art after school. None of it made up for a lack of stimulation in the class for hours each day. Her next move was a full time gifted class for grade 5 which was highly successful but we are now doing a second grade skip at 13 into year 11.
I wish we had done the second grade skip earlier. We considered it from grade 6 to 7 at age 9 but like you worried over the social side. I think we have lost a lot of time.
The skip itself may not generate peers because there still may be no one like your child but at least he will have the satisfaction of stimulation and challenge and working with kids at a similar level of academic achievement. If it doesn't work you will need to seek another solution like homeschooling etc.
Leaving our DD unstimulated didn't help her make friends, it just made her depressed, stop reading and stop participating. She has friends now and in the grade to which she will skip.
